Backport from WordPress core: Improvements for the post format query loop filter

[carolinan]

What? Why? How?

This pull request copies changes that were made in WordPress core in WordPress/wordpress-develop#7314 The pull request that added the PHP changes related to #64167

• Improved logic for the use of the AND relation key when a user queries for both a format and a taxonomy.
• Improved inline documentation, for clarity and readability.
• Improved validation of the queried formats against the registered formats.
• Misc: renaming of variables for better readability.

Testing Instructions

Confirm that there are no issues and no functional changes when using the post format filter with and without the plugin active, using WordPress 6.7 Beta.

To test the functionality:

Enable post formats in a theme by adding the theme support. Example:

function twentytwentyfour_setup(){
	add_theme_support( 'post-formats', array( 'standard', 'aside', 'gallery', 'audio', 'video', 'link', 'image', 'chat', 'status', 'quote' ) );
}

add_action( 'after_setup_theme', 'twentytwentyfour_setup' )

Create a new category.
Create a new post with a post format and assign it to the category.
Create a second post with the same post format, without the category.

Select or insert a query loop block.
In the settings sidebar for the query loop, select "custom".
Locate and open the Filter panel.
Enable the format filter, and enter the name of the format you assigned to your posts.
Save
Confirm that the two posts are showing in the query loop in the editor and front.
Go back to the filter panel and enable the taxonomy filter.
Insert the category you assigned to one of the posts.
Confirm that only the post that has both the category and the format shows in the query loop in the editor and front.

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Co-authored-by: carolinan <poena@git.wordpress.org>

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