WP_Theme_JSON_Resolver_Gutenberg::get_user_data_from_custom_post_type uses uncached SQL queries

[xknown]

Description

We noticed a few performance related issues in big multisite WP site related to the uncached queries used in WP_Theme_JSON_Resolver_Gutenberg::get_user_data_from_custom_post_type(). While there's some caching done at the class level, it'd be good to use object caching to avoid unnecessary SQL queries triggered by the call to wp_get_recent_posts.

Step-by-step reproduction instructions

Please run the following snippet in a WP install with Gutenberg installed.

Screenshots, screen recording, code snippet

<?php
require __DIR__ . '/wp-load.php';

$__queries = array();
$__func = function( $query ) use ( &$__queries ) {
        if ( preg_match( '#post_type = \'wp_global_styles\'#', $query ) ) {
                $__queries[] = $query;
        }
        return $query;
};
add_filter( 'query', $__func );
for ( $i = 0; $i < 10; $i++ ) {
        WP_Theme_JSON_Resolver_Gutenberg::get_user_data();
        WP_Theme_JSON_Resolver_Gutenberg::clean_cached_data();
}
var_dump($__queries);

Ideally, we should only do the SQL query once.

Environment info

• WordPress 5.8.2
• Gutenberg 11.8.3 (the latest versions are also affected, and also add more similar code in gutenberg_add_active_global_styles_link)

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes