box/memtx: Skip tuple memory from coredump by default

Quoting feature request

 | Tarantool is Database and Application Server in one box.
 |
 | Appserver development process contains a lot of
 | lua/luajit-ffi/lua-c-extension code.
 |
 | Coredump is very useful in case when some part of appserver crashed.
 | If the reason is input - data from database is not necessary. If the reason
 | is output - data from database is already in snap/xlog files.
 |
 | Therefore consider core dumps without data enabled by default.

For info: the strip_core feature has been introduced in
549140b3

Closes #4337

@TarantoolBot document
Title: Document box.cfg.strip_core

When Tarantool runs under a heavy load the memory allocated
for tuples may be very huge in size and to eliminate this
memory from being present in `coredump` file the `box.cfg.strip_core`
parameter should be set to `true`.

The default value is `true`.

src/box/lua/load_cfg.lua

@@ -25,7 +25,7 @@ end
 local default_cfg = {
     listen              = nil,
     memtx_memory        = 256 * 1024 *1024,
-    strip_core          = false,
+    strip_core          = true,
     memtx_min_tuple_size = 16,
     memtx_max_tuple_size = 1024 * 1024,
     slab_alloc_factor   = 1.05,

test/app-tap/init_script.result

@@ -32,7 +32,7 @@ box.cfg
 27	replication_timeout:1
 28	rows_per_wal:500000
 29	slab_alloc_factor:1.05
-30	strip_core:false
+30	strip_core:true
 31	too_long_threshold:0.5
 32	vinyl_bloom_fpr:0.05
 33	vinyl_cache:134217728

test/box/admin.result

@@ -85,7 +85,7 @@ cfg_filter(box.cfg)
   - - slab_alloc_factor
     - 1.05
   - - strip_core
-    - false
+    - true
   - - too_long_threshold
     - 0.5
   - - vinyl_bloom_fpr

test/box/cfg.result

@@ -73,7 +73,7 @@ cfg_filter(box.cfg)
   - - slab_alloc_factor
     - 1.05
   - - strip_core
-    - false
+    - true
   - - too_long_threshold
     - 0.5
   - - vinyl_bloom_fpr
@@ -174,7 +174,7 @@ cfg_filter(box.cfg)
   - - slab_alloc_factor
     - 1.05
   - - strip_core
-    - false
+    - true
   - - too_long_threshold
     - 0.5
   - - vinyl_bloom_fpr