Multisite: Bump `last_changed` cache on site update and creation

When a site is added, updated, or deleted, the `site_ids` cache for a query will no longer be reliable. Bumping `last_changed` will force a new query for site IDs.

See #35791.


git-svn-id: https://develop.svn.wordpress.org/trunk@37618 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/ms-blogs.php

@@ -465,6 +465,8 @@ function clean_blog_cache( $blog ) {
 	 * @param string  $domain_path_key md5 hash of domain and path.
 	 */
 	do_action( 'clean_site_cache', $blog_id, $blog, $domain_path_key );
+
+	wp_cache_set( 'last_changed', microtime(), 'sites' );
 }
 
 /**

src/wp-includes/ms-functions.php

@@ -1147,6 +1147,8 @@ function wpmu_create_blog( $domain, $path, $title, $user_id, $meta = array(), $s
 	 */
 	do_action( 'wpmu_new_blog', $blog_id, $user_id, $domain, $path, $site_id, $meta );
 
+	wp_cache_set( 'last_changed', microtime(), 'sites' );
+
 	return $blog_id;
 }