Frozen indices are deprecated which makes all the [SQL features supporting frozen indices](https://www.elastic.co/guide/en/elasticsearch/reference/current/sql-index-frozen.html) obsolete.

This includes:

* `index_include_frozen` request parameter in the `_sql` endpoint
* `index.include.frozen` (J|O)DBC driver settings
* `SHOW TABLES INCLUDE FROZEN` queries and the `FROZEN INDEX` kind in the corresponding response
* The `FROZEN` modifier in `FROM` clauses (as in `SELECT * FROM FROZEN archive`)

`_search` raises a deprecation warning when frozen indices are being searched with `ignore_throttled=false`. SQL could do the same when the `index_include_frozen` request parameter is set or when the `FROZEN` keyword is used.

Relates to https://github.com/elastic/elasticsearch/issues/70192
x-pack/plugin/sql/sql-action/src/main/java/org/elasticsearch/xpack/sql/action/SqlQueryRequest.java
/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0; you may not use this file except in compliance with the Elastic License
 * 2.0.
 */
package org.elasticsearch.xpack.sql.action;
import org.elasticsearch.Version;
import org.elasticsearch.action.ActionRequestValidationException;
import org.elasticsearch.common.Strings;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;