Multisite/Sites: Add links to filter websites by status.

This commit brings the Network-Admin Sites list page up-to-speed with other similar list-table powered pages, by adding links to filter the results by Site Status.

Includes a single unit test for the newly introduced `wp_count_sites()` multisite function, named to match the `wp_count_` function pattern from other list tables.

Fixes #37392. Props mnelson4, spacedmonkey, pbiron.


Built from https://develop.svn.wordpress.org/trunk@46251


git-svn-id: http://core.svn.wordpress.org/trunk@46063 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/network/sites.php

@@ -369,6 +369,8 @@ if ( isset( $_REQUEST['s'] ) && strlen( $_REQUEST['s'] ) ) {
 
 <hr class="wp-header-end">
 
+<?php $wp_list_table->views(); ?>
+
 <?php echo $msg; ?>
 
 <form method="get" id="ms-search" class="wp-clearfix">