Multisite: Move site-specific metadata integrations from the wrapper functions to the low-level Meta API functions.

This complements the work in [43729] and prepares site metadata for future REST API support.

Props spacedmonkey.
Fixes #45091. See #44467.


git-svn-id: https://develop.svn.wordpress.org/trunk@44468 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/schema.php

@@ -1329,5 +1329,5 @@ function populate_site_meta( $site_id, array $meta = array() ) {
 
 	$wpdb->query( "INSERT INTO $wpdb->blogmeta ( blog_id, meta_key, meta_value ) VALUES " . $insert ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
 
-	wp_cache_set( 'last_changed', microtime(), 'sites' );
+	wp_cache_set_sites_last_changed();
 }