Update luacheckrc to suppress all warnings from lua vars with `_` prefix.
This allows to declare a function with an expected standardized interface
without unused var warning.
Fix luacheck warnings in src/box/console.lua.

Closes #5032

NO_CHANGELOG=warning fix
NO_DOC=warning fix
NO_TEST=warning fix

Running of luacheck against test-run submodule is redundant.
Add dedicated bypass to .luacheckrc.

NO_DOC=ci
NO_CHANGELOG=ci
NO_TEST=ci

There are different warnings after adding checks and luatest submodules.

Follows-up tarantool/test-run#304

Currently getting iproto statistics per thread is possible only
in debug mode, using `ERRINJ_IPROTO_SINGLE_THREAD_STAT` (it can be
used only in tests). This way have several disadvantages: first of
all `errinj` is not a place to get statistics, secondly user may be
interested in getting iproto statistics per thread. In this patch
`box.stat.net.thread` was implemented, it can be used for getting
same statistics as from `box.stat.net` but per thread.

Part of #6293

@TarantoolBot document
Title: getting network statistic per thread was implemented
User has possibility to run several iproto threads, but at the moment
he can get only general statistics, which combines statistics for all
threads. Now `box.stat.net.thread` has been implemented to get the same
statistics as when using `box.stat.net`, but for a thread. User can call
`box.stat.net.thread()` as a function to get general network statistics
per threads. For example for two iproto threads:
---
- - SENT:
      total: 0
      rps: 0
    CONNECTIONS:
      current: 0
      rps: 0
      total: 0
    REQUESTS:
      current: 0
      rps: 0
      total: 0
    RECEIVED:
      total: 0
      rps: 0
  - SENT:
      total: 0
      rps: 0
    CONNECTIONS:
      current: 0
      rps: 0
      total: 0
    REQUESTS:
      current: 0
      rps: 0
      total: 0
    RECEIVED:
      total: 0
      rps: 0
...

Also user can indexed it as a table by thread number. For example
`box.stat.net.thread[1]` returns network statistics for first iproto
thread:
---
- SENT:
    total: 0
    rps: 0
  CONNECTIONS:
    current: 0
    rps: 0
    total: 0
  REQUESTS:
    current: 0
    rps: 0
    total: 0
  RECEIVED:
    total: 0
    rps: 0
...

There are users that have specific workloads where iproto thread
is the bottleneck of throughput: iproto thread's code is 100% loaded
while TX thread's core is not. For such cases it would be nice to have
a capability to create several iproto threads.

Closes #5645

@TarantoolBot document
Title: implement ability to run multiple iproto threads
Implement ability to run multiple iproto threads, which is useful
in some specific workloads where iproto thread is the bottleneck
of throughput. To specify count of iproto threads, user should used
iproto_threads option in box.cfg. For example if user want to start
8 iproto threads, he must enter `box.cfg{iproto_threads=8}`. Default
iproto threads count == 1. This option is not dynamic, so user can't
change it after first setting, until server restart. Distribution of
connections per threads is managed by OS kernel.

List of changes in test-run:

* readme: add memcached to users ([PR #285][1])
* test: add integration tests ([PR #273][2])
* test: enable in continuous integration ([PR #273][2])
* Fix slowdown on Python 3 ([PR #290][3])

Updated .luacheckrc to exclude newly added 'core = tarantool' tests
(ones that check test-run itself).

[1]: https://github.com/tarantool/test-run/pull/285
[2]: https://github.com/tarantool/test-run/pull/273
[3]: https://github.com/tarantool/test-run/pull/290

This commit updates test-run with an update of tarantool-python, which
eliminates the test-run submodule from tarantool-python. In other words,
we have no test-run submodule inside test-run anymore.

The goal is to don't confuse luacheck with old revisions of test-run /
tarantool-python code and to make recursive clone faster. See [1] and
[2] for details.

[1]: https://github.com/tarantool/test-run/pull/268
[2]: https://github.com/tarantool/tarantool-python/commit/dccf18fd07ac684195fdd386d2a5285b9582d380

W611 (A line consists of nothing but whitespace)

Note: changes were made automatically in vim with regexp "%s/^\s*$//g".

Closes #5739

Closes #5464

W621 (Inconsistent indentation (SPACE followed by TAB))

Part of #5464

W612 (A line contains trailing whitespace)
W613 (Trailing whitespace in a string)
W614 (Trailing whitespace in a comment)

Note: changes were made automatically in vim with regexp "%s/\s\+$//e".

Part of #5464

W542 (An empty if branch)

Part of #5464

W512 (Loop can be executed at most once)

Part of #5464

W511 (Unreachable code)

Part of #5464

W311 (Value assigned to a local variable is unused)

Part of #5464

W231 (Local variable is set but never accessed)

Part of #5464

W213 (Unused loop variable)

Part of #5464

W212 (Unused argument)

Part of #5464

W211 (Unused local variable)

Part of #5464

W113 (Accessing an undefined global variable)

Part of #5464

LuaJIT submodule is bumped to introduce the following changes:
* test: run luacheck static analysis via CMake
* test: fix warnings found with luacheck in misclib*
* test: run LuaJIT tests via CMake
* build: replace GNU Make with CMake
* build: preserve the original build system

Since LuaJIT build system is ported to CMake in scope of the changeset
mentioned above, the module building the LuaJIT bundled in Tarantool is
completely reworked. There is no option to build Tarantool against
another prebuilt LuaJIT due to a91962c0
('Until Bug#962848 is fixed, don't try to compile with external
LuaJIT'), so all redundant options defining the libluajit to be used in
Tarantool are dropped with the related auxiliary files.

To run LuaJIT related tests or static analysis for Lua files within
LuaJIT repository, <LuaJIT-test> and <LuaJIT-luacheck> targets are used
respectively as a dependency of the corresponding Tarantool targets.

As an additional dependency to run LuaJIT tests, prove[1] utility is
required, so the necessary binary packages are added to the lists with
build requirements.

[1]: https://metacpan.org/pod/TAP::Harness#prove



Closes #4862
Closes #5470
Closes #5631

Reviewed-by: Sergey Kaplun <skaplun@tarantool.org>
Reviewed-by: Timur Safin <tsafin@tarantool.org>
Signed-off-by: Igor Munkin <imun@tarantool.org>

Closes #5462

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

Closes #5461

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

Closes #5465

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

Closes #5650

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

Closes #5458

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

Closes #5169

(cherry picked from commit a661bef70d4ff2ba511c6e6ea71e95c6f50beb49)

Closes #5460

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

Closes #5466

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

Closes #5457

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

Closes #5456

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

Closes #5455

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

Closes #5467

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

Closes #5469

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

Closes #5468

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

serpent module has been dropped in commit
b53cb2ae
"console: drop unused serpent module", but comment that belong to module
was left in luacheck config.

Closes #5454

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

Closes #5453

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

Fixed luacheck warning 111 (setting non-standard global variable)
in test/sql-tap directory.
Enabled this directory for checking W111 in
config file(.luacheckrc).

Changed almost all variables in test/sql-tap from globals
to locals. In any cases, where variables need to be global,
added explicit _G. prefix (table of globals).

Fixes #5173
Part-of #5464

Since the commit ae7e2103 we use internal serializer
thus we no longer need serpent code.

The patch removes the references from the source code
and .gitmodules file, still one might need to run

 | git submodule deinit -f third_party/serpent

manually to clean up the working tree depending
on local git version.

Closes #5517

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>