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/storage/ipc/ipci.c

@@ -25,7 +25,6 @@
 #include "access/xlogprefetcher.h"
 #include "access/xlogrecovery.h"
 #include "commands/async.h"
-#include "commands/waitlsn.h"
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "postmaster/autovacuum.h"
@@ -153,7 +152,6 @@ CalculateShmemSize(int *num_semaphores)
 	size = add_size(size, WaitEventExtensionShmemSize());
 	size = add_size(size, InjectionPointShmemSize());
 	size = add_size(size, SlotSyncShmemSize());
-	size = add_size(size, WaitLSNShmemSize());
 #ifdef EXEC_BACKEND
 	size = add_size(size, ShmemBackendArraySize());
 #endif
@@ -359,7 +357,6 @@ CreateOrAttachShmemStructs(void)
 	StatsShmemInit();
 	WaitEventExtensionShmemInit();
 	InjectionPointShmemInit();
-	WaitLSNShmemInit();
 }
 
 /*

src/backend/storage/lmgr/proc.c

@@ -36,7 +36,6 @@
 #include "access/transam.h"
 #include "access/twophase.h"
 #include "access/xlogutils.h"
-#include "commands/waitlsn.h"
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "postmaster/autovacuum.h"
@@ -863,11 +862,6 @@ ProcKill(int code, Datum arg)
 	 */
 	LWLockReleaseAll();
 
-	/*
-	 * Cleanup waiting for LSN if any.
-	 */
-	WaitLSNCleanup();
-
 	/* Cancel any pending condition variable sleep, too */
 	ConditionVariableCancelSleep();