Editor: Add changes for new Comments Query Loop blocks

Backports changes from Gutenberg to add functions required by Comment Query Loop and related blocks. Related unit tests depends on the new blocks and they will get added seperately.

Props darerodz, timothyblynjacobs.
See #55505.



git-svn-id: https://develop.svn.wordpress.org/trunk@53138 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php

@@ -1196,7 +1196,8 @@ class WP_REST_Comments_Controller extends WP_REST_Controller {
 			$rest_url = add_query_arg( $args, rest_url( $this->namespace . '/' . $this->rest_base ) );
 
 			$links['children'] = array(
-				'href' => $rest_url,
+				'href'     => $rest_url,
+				'embedded' => true,
 			);
 		}