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/btr0cur.h

@@ -64,9 +64,6 @@ struct btr_latch_leaves_t {
 #include "row0types.h"
 #include "ha0ha.h"
 
-#define BTR_CUR_ADAPT
-#define BTR_CUR_HASH_ADAPT
-
 #ifdef UNIV_DEBUG
 /*********************************************************//**
 Returns the page cursor component of a tree cursor.
@@ -980,17 +977,19 @@ inherited external field. */
 
 /** Number of searches down the B-tree in btr_cur_search_to_nth_level(). */
 extern ulint	btr_cur_n_non_sea;
-/** Number of successful adaptive hash index lookups in
-btr_cur_search_to_nth_level(). */
-extern ulint	btr_cur_n_sea;
 /** Old value of btr_cur_n_non_sea.  Copied by
 srv_refresh_innodb_monitor_stats().  Referenced by
 srv_printf_innodb_monitor(). */
 extern ulint	btr_cur_n_non_sea_old;
+#ifdef BTR_CUR_HASH_ADAPT
+/** Number of successful adaptive hash index lookups in
+btr_cur_search_to_nth_level(). */
+extern ulint	btr_cur_n_sea;
 /** Old value of btr_cur_n_sea.  Copied by
 srv_refresh_innodb_monitor_stats().  Referenced by
 srv_printf_innodb_monitor(). */
 extern ulint	btr_cur_n_sea_old;
+#endif /* BTR_CUR_HASH_ADAPT */
 
 #ifdef UNIV_DEBUG
 /* Flag to limit optimistic insert records */