Add missing post create and alter hooks to policy objects.

AlterPolicy() and CreatePolicy() lacked their respective hook invocations.
Noted by Noah Misch, review by Dean Rasheed. Back-patch to 9.5 where
RLS was introduced.

src/backend/commands/policy.c

@@ -629,6 +629,8 @@ CreatePolicy(CreatePolicyStmt *stmt)
 									 SHARED_DEPENDENCY_POLICY);
 	}
 
+	InvokeObjectPostCreateHook(PolicyRelationId, policy_id, 0);
+
 	/* Invalidate Relation Cache */
 	CacheInvalidateRelcache(target_table);
 
@@ -860,6 +862,8 @@ AlterPolicy(AlterPolicyStmt *stmt)
 									 SHARED_DEPENDENCY_POLICY);
 	}
 
+	InvokeObjectPostAlterHook(PolicyRelationId, policy_id, 0);
+
 	heap_freetuple(new_tuple);
 
 	/* Invalidate Relation Cache */