Use errmsg_internal for debug messages

An inconsistent set of debug-level messages was not using
errmsg_internal(), thus uselessly exposing the messages to translation
work.  Fix those.

src/backend/storage/lmgr/predicate.c

@@ -1602,7 +1602,7 @@ GetSafeSnapshot(Snapshot origSnapshot)
 		/* else, need to retry... */
 		ereport(DEBUG2,
 				(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-				 errmsg("deferrable snapshot was unsafe; trying a new one")));
+				 errmsg_internal("deferrable snapshot was unsafe; trying a new one")));
 		ReleasePredicateLocks(false, false);
 	}
 

src/backend/storage/lmgr/proc.c

@@ -1413,13 +1413,13 @@ ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
 					initStringInfo(&logbuf);
 					DescribeLockTag(&locktagbuf, &locktag_copy);
 					appendStringInfo(&logbuf,
-									 _("Process %d waits for %s on %s."),
+									 "Process %d waits for %s on %s.",
 									 MyProcPid,
 									 GetLockmodeName(lockmethod_copy, lockmode),
 									 locktagbuf.data);
 
 					ereport(DEBUG1,
-							(errmsg("sending cancel to blocking autovacuum PID %d",
+							(errmsg_internal("sending cancel to blocking autovacuum PID %d",
 									pid),
 							 errdetail_log("%s", logbuf.data)));
 

src/backend/storage/smgr/md.c

@@ -983,7 +983,7 @@ register_dirty_segment(SMgrRelation reln, ForkNumber forknum, MdfdVec *seg)
 	if (!RegisterSyncRequest(&tag, SYNC_REQUEST, false /* retryOnError */ ))
 	{
 		ereport(DEBUG1,
-				(errmsg("could not forward fsync request because request queue is full")));
+				(errmsg_internal("could not forward fsync request because request queue is full")));
 
 		if (FileSync(seg->mdfd_vfd, WAIT_EVENT_DATA_FILE_SYNC) < 0)
 			ereport(data_sync_elevel(ERROR),

src/backend/storage/sync/sync.c

@@ -419,7 +419,7 @@ ProcessSyncRequests(void)
 				else
 					ereport(DEBUG1,
 							(errcode_for_file_access(),
-							 errmsg("could not fsync file \"%s\" but retrying: %m",
+							 errmsg_internal("could not fsync file \"%s\" but retrying: %m",
 									path)));
 
 				/*