box: finish client fibers on shutdown

In the process of graceful shutdown it is convenient to first finish
all client (non system) fibers. Otherwise we should be ready for any
subsystem to handle request from client fiber during or after subsystem
shutdown. This would make code more complex.

We first cancel client fibers and then wait for their finishing. The
fiber may not respond to cancel and hang which cause shutdown hang
but this is the approach we choose for iproto shutdown already.

Note that as a result of this approach application will panic if
it is shutdown during execution of initialization script (in
particular if this script is doing box.cfg).

There are changes in application/test to adopt to client fibers
shutdown:

- make code cancellable (only to pass existing tests, we did not
  investigate all the possible places that should be made such).

- make console stop sending echo to client before client fibers
  shutdown. Otherwise as console server fiber is client one we will send
  message that fiber is cancelled on shutdown which breaks a lot of
  existing tests. This approach is on par with iproto shutdown.

- some tests (7743, replication-luatest/shutdown, replication/anon,
  replication/force_recovery etc etc) test shutdown during execution of
  init script. Now panic is expected so change them accordingly.

- some tests (8530, errinj_vylog) use injection that block client
  fiber finishing. In that tests we don't need graceful shutdown so
  let's just kill tarantool instead.

- we change test in vinyl/errinj for gh-3225. We don't really need
  to check when vinyl reader is blocked as it executes small tasks
  (we assume reading syscall will not hang). Also change test for
  vinyl dump shutdown by slowing dump down instead of blocking it
  entirely. This is required to finish in time client fibers in
  the test.

- other similar changes

Also we can drop code from replication shutdown which is required to
handle client requests during/after shutdown.

Part of #8423

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