Fix query hint retrieval with utilities

Query jumbling is possible in PostgreSQL 16 for utilities, generating a
JumbleState that could involve a query normalization.  This would break
the retrieval of query hints for quite a few scenarios, we we should try
to get the hints from the query planned, mostly around EXPLAIN:
- EXPLAIN EXECUTE
- EXPLAIN CTAS

This commit patches the post parse-analyze hook to ignore entirely
utility queries, unbreaking all the remaining regression tests.

At this point, the regression tests are stable with PostgreSQL 16.

Per pull request #130.

pg_hint_plan.c

@@ -2985,6 +2985,17 @@ pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query,
 	if (plpgsql_recurse_level == 0)
 		current_hint_retrieved = false;
 
+	/*
+	 * Query jumbling is possible with utility queries in PostgreSQL 16 and
+	 * newer versions, hence just leave in this case.  There could be a point
+	 * in providing hints for some cases, like a CTAS or a matview creation,
+	 * but that should not matter much in practice compared to SELECT and DML
+	 * queries, and nobody has made a case for these now.  So let's just
+	 * ignore the case entirely for now.
+	 */
+	if (query->utilityStmt)
+		return;
+
 	/*
 	 * Jumble state is required when hint table is used.  This is the only
 	 * chance to have one already generated in-core.  If it's not the case, no