Revert MAINTAIN privilege and pg_maintain predefined role.

This reverts the following commits: 4dbdb82513, c2122aae63,
5b1a879943, 9e1e9d6560, ff9618e82a, 60684dd834, 4441fc704d,
and b5d6382496.  A role with the MAINTAIN privilege may be able to
use search_path tricks to escalate privileges to the table owner.
Unfortunately, it is too late in the v16 development cycle to apply
the proposed fix, i.e., restricting search_path when running
maintenance commands.

Bumps catversion.

Reviewed-by: Jeff Davis
Discussion: https://postgr.es/m/E1q7j7Y-000z1H-Hr%40gemulon.postgresql.org
Backpatch-through: 16

src/backend/commands/matview.c

@@ -165,8 +165,7 @@ ExecRefreshMatView(RefreshMatViewStmt *stmt, const char *queryString,
 	 */
 	matviewOid = RangeVarGetRelidExtended(stmt->relation,
 										  lockmode, 0,
-										  RangeVarCallbackMaintainsTable,
-										  NULL);
+										  RangeVarCallbackOwnsTable, NULL);
 	matviewRel = table_open(matviewOid, NoLock);
 	relowner = matviewRel->rd_rel->relowner;