MDEV-7660 - MySQL WL#6671 "Improve scalability by not using thr_lock.c locks

for InnoDB tables"

Don't use thr_lock.c locks for InnoDB tables. Below is list of changes that
were needed to implement this:
- HANDLER OPEN acquireis MDL_SHARED_READ instead of MDL_SHARED
- HANDLER READ calls external_lock() even if SE is not going to be locked by
  THR_LOCK
- InnoDB lock wait timeouts are now honored which are much shorter by default
  than server lock wait timeouts (1 year vs 50 seconds)
- with @@autocommit= 1 LOCK TABLES disables autocommit implicitely, though
  user still sees @@autocommt= 1
- the above starts implicit transaction
- transactions started by LOCK TABLES are now rolled back on disconnect
  (previously everything was committed due to autocommit)
- transactions started by LOCK TABLES are now rolled back by ROLLBACK
  (previously everything was committed due to autocommit)
- it is now impossible to change BINLOG_FORMAT under LOCK TABLES (at least
  to statement) due to running transaction
- LOCK TABLES WRITE is additionally handled by MDL
- ...in contrast LOCK TABLES READ protection against DML is pure InnoDB
- combining transactional and non-transactional tables under LOCK TABLES
  may cause rolled back changes in transactional table and "committed"
  changes in non-transactional table
- user may disable innodb_table_locks, which will cause LOCK TABLES to be
  noop basically

Removed tests for BUG#45143 and BUG#55930 which cover InnoDB + THR_LOCK. To
operate properly these tests require code flow to go through THR_LOCK debug
sync points, which is not the case after this patch. These tests are removed
by WL#6671 as well. An alternative is to port them to different storage engine.

mysql-test/include/mtr_warnings.sql

@@ -205,14 +205,6 @@ INSERT INTO global_suppressions VALUES
  ("==[0-9]*== Warning: invalid file descriptor -1 in syscall write()"),
  ("==[0-9]*== Warning: invalid file descriptor -1 in syscall read()"),
 
- /*
-   BUG#42147 - Concurrent DML and LOCK TABLE ... READ for InnoDB 
-   table cause warnings in errlog
-   Note: This is a temporary suppression until Bug#42147 can be 
-   fixed properly. See bug page for more information.
-  */
- ("Found lock of type 6 that is write and read locked"),
-
  /*
    Transient network failures that cause warnings on reconnect.
    BUG#47743 and BUG#47983.