WP_REST_Pattern_Directory_Controller::get_items doesn't support array arguments

[antonvlasenko]

Since http://api.wordpress.org/patterns API supports array parameters, there is no need to implode slug values inside the _register_remote_theme_patterns function.
Both WP_REST_Pattern_Directory_Controller and _register_remote_theme_patternsmust be updated to support array request arguments.

Trac ticket: https://core.trac.wordpress.org/ticket/55574

[antonvlasenko]

Steps to test the PR:

1. Activate a block-based theme like Twenty Twenty-Two.
2. Open the theme.json file for that theme and add a new patterns setting to it:

   "patterns": [
   	"short-text-surrounded-by-round-images",
   	"visual-navigation-with-rainbow-gradient"
     ],
   

You can use any pattern instead of the patterns above. However, it's important to use at least 2 patterns.
A list of available patterns can be found here: ​https://wordpress.org/patterns/

3. Make a GET call to this REST API endpoint:

/wp/v2/block-patterns/patterns
Expected result:
The response must contact patterns added in step 2.
E.g.:

[antonvlasenko]

This task is a follow-up to ​https://github.com/WordPress/wordpress-develop/pull/2488#pullrequestreview-936828609

[gziolo]

In 53218:

REST API: Add array argument to getItems for Pattern Directory endopoint

Since ​http://api.wordpress.org/patterns API supports array parameters, there is no need to implode slug values inside the _register_remote_theme_patterns function.
Both WP_REST_Pattern_Directory_Controller and _register_remote_theme_patternsmust be updated to support array request arguments.

Props antonvlasenko.
Fixes #55574.
Follow-up #55505, [53152].

Committed with https://core.trac.wordpress.org/changeset/53218.