pgsql: Fix _bt_allequalimage() call within critical section.

Fix _bt_allequalimage() call within critical section. _bt_allequalimage() does complicated things, so it's not OK to call it in a critical section. Per buildfarm failure on 'prion', which uses -DRELCACHE_FORCE_RELEASE -DCATCACHE_FORCE_RELEASE options. Discussion: https://www.postgresql.org/messa

pgsql: Fix _bt_allequalimage() call within critical section.

Fix _bt_allequalimage() call within critical section. _bt_allequalimage() does complicated things, so it's not OK to call it in a critical section. Per buildfarm failure on 'prion', which uses -DRELCACHE_FORCE_RELEASE -DCATCACHE_FORCE_RELEASE options. Discussion: https://www.postgresql.org/messa