MDEV-26779: Enable adaptive spinning on ARMv8 for lock_sys.wait_mutex

Similar to commit f7684f0c (MDEV-26855)
we will try to enable the adaptive spinloop for lock_sys.wait_mutex
on ARMv8.

Enabling any form of spinloop for lock_sys.wait_mutex did not show a
significant improvement in our tests on AMD64.

Spinning can be argued to be a hack to reduce the impact on mutex
contention. It would be better to adjust the code to reduce
contention in the first place.

storage/innobase/lock/lock0lock.cc

@@ -391,7 +391,11 @@ void lock_sys_t::create(ulint n_cells)
   m_initialised= true;
 
   latch.SRW_LOCK_INIT(lock_latch_key);
+#ifdef __aarch64__
+  mysql_mutex_init(lock_wait_mutex_key, &wait_mutex, MY_MUTEX_INIT_FAST);
+#else
   mysql_mutex_init(lock_wait_mutex_key, &wait_mutex, nullptr);
+#endif
 #ifdef SUX_LOCK_GENERIC
   pthread_mutex_init(&hash_mutex, nullptr);
   pthread_cond_init(&hash_cond, nullptr);