REST API: Bring new endpoints for Block Patterns from Gutenberg plugin

Related Gutenberg issue: https://github.com/WordPress/gutenberg/issues/39889.

Backporting changes from the Gutenberg plugin:
- new Block Patterns REST API endpoint
- new Block Pattern Categories REST API endpoint
- updates to Query Loop related patterns
- support for custom taxonomies in Query Loop block

Props hellofromtonya, peterwilsoncc, ntsekouras, zieladam, ironprogrammer, spacedmonkey, timothyblynjacobs, antonvlasenko, jsnajdr.
See #55505.




git-svn-id: https://develop.svn.wordpress.org/trunk@53152 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/rest-api.php

@@ -337,6 +337,14 @@ function create_initial_rest_routes() {
 	$controller = new WP_REST_Pattern_Directory_Controller();
 	$controller->register_routes();
 
+	// Block Patterns.
+	$controller = new WP_REST_Block_Patterns_Controller();
+	$controller->register_routes();
+
+	// Block Pattern Categories.
+	$controller = new WP_REST_Block_Pattern_Categories_Controller();
+	$controller->register_routes();
+
 	// Site Health.
 	$site_health = WP_Site_Health::get_instance();
 	$controller  = new WP_REST_Site_Health_Controller( $site_health );