Add filter to remove unavailable terms from facet

[burhandodhy]

Description of the Change

This PR introduces the new filter ep_facet_taxonomy_terms that allows filtering the list of terms in Fact. By using this filter, the user can remove the unavailable terms from the facet. Previously suggested solution has an issue that shows the search box even the available terms are lower than the threshold.

Example: The below code will remove the unavailable terms from facet

add_filter( 'ep_facet_taxonomy_terms', function ( $terms, $taxonomy ) {

	$filtered_terms = array_filter( $terms, function( $term ) {
		return $term->count > 0 ;
	} );

	return $filtered_terms;
}, 10, 2 );

Closes #2760

How to test the Change

• Add the above code in theme functions.php
• Add the Facet block in widgets
• Search for any term and it will only show those terms which are available.

Changelog Entry

Added - ep_facet_taxonomy_terms filter to filter the Facet terms

Credits

Props @burhandodhy

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.