Based on the performance testing that was conducted in MDEV-17492,
the InnoDB adaptive hash index could only help performance in specific,
almost-read-only workloads. It could slow down all kinds of workloads
(especially DROP TABLE, TRUNCATE TABLE, ALTER TABLE, or DROP INDEX
operations), and it can become corrupted, causing crashes
and possibly data corruption. Furthermore, the adaptive hash index
consumes space from the InnoDB buffer pool, which could hurt performance
when the working set would almost fit in the buffer pool.

Given all this, it is best to remove innodb_adaptive_hash_index.
For now, we will change the default value of the build option
WITH_INNODB_AHI to OFF and adjust tests.

The test rpl.rpl_failed_drop_tbl_binlog depends on DROP TABLE being
able to be interrupted while it is dropping pages from the
adaptive hash index. It will be skipped from now on by default,
but it will be tested for builds WITH_INNODB_AHI=ON.