Sync: remove extension on legacy class (#14909)

* Sync: remove extension on legacy class

In #14906 were seeing that adding a new parameter to a Sync class
causes legacy classes to complain.

We can fix this by having the legacy class be isolated, and not
extending the new class.

* Sync: updating legacy class

When ever we update methods in sync, we also need to update the legacy methods.
Because the legacy method extends it successor.

packages/compat/legacy/class-jetpack-sync-actions.php

@@ -114,12 +114,14 @@ public static function set_is_importing_true() {
 	 * @param Integer $queue_id the queue identifier.
 	 * @param Integer $checkout_duration time spent retrieving items.
 	 * @param Integer $preprocess_duration Time spent converting items into data.
+	 * @param Integer $queue_size The current size of the sync queue.
+	 *
 	 * @return WP_Response the response object.
 	 */
-	public static function send_data( $data, $codec_name, $sent_timestamp, $queue_id, $checkout_duration, $preprocess_duration ) {
+	public static function send_data( $data, $codec_name, $sent_timestamp, $queue_id, $checkout_duration, $preprocess_duration, $queue_size = null ) {
 		_deprecated_function( __METHOD__, 'jetpack-7.5', 'Automattic\Jetpack\Sync\Actions' );
 
-		return Actions::send_data( $data, $codec_name, $sent_timestamp, $queue_id, $checkout_duration, $preprocess_duration );
+		return Actions::send_data( $data, $codec_name, $sent_timestamp, $queue_id, $checkout_duration, $preprocess_duration, $queue_size );
 	}
 
 	/**