Make pg_restore's identify_locking_dependencies() more bulletproof.

This function had a blacklist of dump object types that it believed
needed exclusive lock ... but we hadn't maintained that, so that it
was missing ROW SECURITY, POLICY, and INDEX ATTACH items, all of
which need (or should be treated as needing) exclusive lock.

Since the same oversight seems likely in future, let's reverse the
sense of the test so that the code has a whitelist of safe object
types; better to wrongly assume a command can't be run in parallel
than the opposite.  Currently the only POST_DATA object type that's
safe is CREATE INDEX ... and that list hasn't changed in a long time.

Back-patch to 9.5 where RLS came in.

Discussion: https://postgr.es/m/11450.1535483506@sss.pgh.pa.us

src/bin/pg_dump/pg_backup_archiver.c

@@ -4589,16 +4589,24 @@ identify_locking_dependencies(ArchiveHandle *AH, TocEntry *te)
 	int			nlockids;
 	int			i;
 
+	/*
+	 * We only care about this for POST_DATA items.  PRE_DATA items are not
+	 * run in parallel, and DATA items are all independent by assumption.
+	 */
+	if (te->section != SECTION_POST_DATA)
+		return;
+
 	/* Quick exit if no dependencies at all */
 	if (te->nDeps == 0)
 		return;
 
-	/* Exit if this entry doesn't need exclusive lock on other objects */
-	if (!(strcmp(te->desc, "CONSTRAINT") == 0 ||
-		  strcmp(te->desc, "CHECK CONSTRAINT") == 0 ||
-		  strcmp(te->desc, "FK CONSTRAINT") == 0 ||
-		  strcmp(te->desc, "RULE") == 0 ||
-		  strcmp(te->desc, "TRIGGER") == 0))
+	/*
+	 * Most POST_DATA items are ALTER TABLEs or some moral equivalent of that,
+	 * and hence require exclusive lock.  However, we know that CREATE INDEX
+	 * does not.  (Maybe someday index-creating CONSTRAINTs will fall in that
+	 * category too ... but today is not that day.)
+	 */
+	if (strcmp(te->desc, "INDEX") == 0)
 		return;
 
 	/*