Editor: Add `excerpt` support to the `wp_block` post type.

The purpose is to enable using the excerpt as a description for user-created patterns on the Site Editor Pattern screens.

This commit backports the original PR from Gutenberg repository:
* [[https://github.com/WordPress/gutenberg/pull/60549|#60549: [Data Views] User patterns: Use excerpt as description]]

Reference: [[https://github.com/WordPress/gutenberg/issues/55244|#55244: Patterns: Add descriptions to user-created patterns]].

Follow-up to [44146], [44150], [50835], [56030].

Props poena, ntsekouras, krupalpanchal.
Fixes #61250.
Built from https://develop.svn.wordpress.org/trunk@58184


git-svn-id: http://core.svn.wordpress.org/trunk@57647 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/post.php

@@ -328,6 +328,7 @@ function create_initial_post_types() {
 			'map_meta_cap'          => true,
 			'supports'              => array(
 				'title',
+				'excerpt',
 				'editor',
 				'revisions',
 				'custom-fields',

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.6-alpha-58183';
+$wp_version = '6.6-alpha-58184';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.