Revert: Implement pg_wal_replay_wait() stored procedure

This commit reverts 06c418e163, e37662f221, bf1e650806, 25f42429e2,
ee79928441, and 74eaf66f98 per review by Heikki Linnakangas.

Discussion: https://postgr.es/m/b155606b-e744-4218-bda5-29379779da1a%40iki.fi

src/backend/commands/meson.build

@@ -50,5 +50,4 @@ backend_sources += files(
   'vacuumparallel.c',
   'variable.c',
   'view.c',
-  'waitlsn.c',
 )