MDEV-12121 Introduce build option WITH_INNODB_AHI to disable innodb_adaptive_hash_index

The InnoDB adaptive hash index is sometimes degrading the performance of
InnoDB, and it is sometimes disabled to get more consistent performance.
We should have a compile-time option to disable the adaptive hash index.

Let us introduce two options:

OPTION(WITH_INNODB_AHI "Include innodb_adaptive_hash_index" ON)
OPTION(WITH_INNODB_ROOT_GUESS "Cache index root block descriptors" ON)

where WITH_INNODB_AHI always implies WITH_INNODB_ROOT_GUESS.

As part of this change, the misleadingly named function
trx_search_latch_release_if_reserved(trx) will be replaced with the macro
trx_assert_no_search_latch(trx) that will be empty unless
BTR_CUR_HASH_ADAPT is defined (cmake -DWITH_INNODB_AHI=ON).

We will also remove the unused column
INFORMATION_SCHEMA.INNODB_TRX.TRX_ADAPTIVE_HASH_TIMEOUT.
In MariaDB Server 10.1, it used to reflect the value of
trx_t::search_latch_timeout which could be adjusted during
row_search_for_mysql(). In 10.2, there is no such field.

Other than the removal of the unused column TRX_ADAPTIVE_HASH_TIMEOUT,
this is an almost non-functional change to the server when using the
default build options.

Some tests are adjusted so that they will work with both
-DWITH_INNODB_AHI=ON and -DWITH_INNODB_AHI=OFF. The test
innodb.innodb_monitor has been renamed to innodb.monitor
in order to track MySQL 5.7, and the duplicate tests
sys_vars.innodb_monitor_* are removed.

storage/innobase/include/trx0i_s.h

@@ -162,8 +162,10 @@ struct i_s_trx_row_t {
 					/*!< check_foreigns in trx_t */
 	const char*	trx_foreign_key_error;
 					/*!< detailed_error in trx_t */
+#ifdef BTR_CUR_HASH_ADAPT
 	ibool		trx_has_search_latch;
 					/*!< has_search_latch in trx_t */
+#endif /* BTR_CUR_HASH_ADAPT */
 	ulint		trx_is_read_only;
 					/*!< trx_t::read_only */
 	ulint		trx_is_autocommit_non_locking;