A performance regression was introduced by
commit e71e6133 (MDEV-24671)
and mostly addressed by
commit 455514c8.

The regression is likely caused by increased contention
lock_sys.latch (former lock_sys.mutex), possibly indirectly
caused by contention on lock_sys.wait_mutex. This change aims to
reduce both, but further improvements will be needed.

lock_wait(): Minimize the lock_sys.wait_mutex hold time.

lock_sys_t::deadlock_check(): Add a parameter for indicating
whether lock_sys.latch is exclusively locked.

trx_t::was_chosen_as_deadlock_victim: Always use atomics.

lock_wait_wsrep(): Assume that no mutex is being held.

Deadlock::report(): Always kill the victim transaction.

lock_sys_t::timeout: New counter to back MONITOR_TIMEOUT.