feat/3954: Add filters to exclude post types and taxonomy terms from Instant Results

[Sidsector9]

Description of the Change

• Adds ep_instant_results_excluded_post_types filter to exclude post types and related posts from Instant Results.
• Adds ep_instant_results_excluded_term_ids filter to exclude taxonomy terms from Instant Results facets.

Post Type Exclusion (ep_instant_results_excluded_post_types)

Excluded post types are removed from both the Post Type facet and the search template itself. This means content of that type will not appear in Instant Results at all.

The search template is regenerated when Instant Results settings are saved, when the weighting configuration is saved, and after a full sync. So after changing this filter, save either settings screen, run a sync, or run wp elasticpress put-search-template, otherwise the old template stays in use.

add_filter( 'ep_instant_results_excluded_post_types', function( $excluded ) {
    $excluded[] = 'page';
    return $excluded;
} );

Term Exclusion (ep_instant_results_excluded_term_ids)

Excluded terms are hidden from every taxonomy facet (Category, Tag, etc.) but posts associated with those terms still appear in search results. This is intentional, a post can belong to multiple terms, so excluding a term from the facet should not remove posts that also match through other, non-excluded terms.

add_filter( 'ep_instant_results_excluded_term_ids', function( $excluded ) {
    $excluded[] = 1; // Uncategorized
    return $excluded;
} );

Closes #3954

Changelog Entry

Added: ep_instant_results_excluded_post_types filter to exclude post types from Instant Results facets and search results.
Added: ep_instant_results_excluded_term_ids filter to exclude taxonomy terms from Instant Results facets.

Credits

Props @feliciaoctocog, @Sidsector9

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added Critical Flows, Test Cases, and/or End-to-End Tests to cover my change.
• All new and existing tests pass.

[felipeelia]

We will need tests for this one, @Sidsector9.

[Sidsector9]

@felipeelia the tests have been added 👍

[felipeelia]

@Sidsector9 We will need to replace all the 5.4.0 with 5.3.4. In addition to that, can you please change get_excluded_post_types and get_excluded_term_ids returns, so we always make sure they are sending the correct types back to the caller?

Something like array_filter( array_map( 'absint', (array) apply_filters( 'ep_instant_results_excluded_term_ids', [] ) ) );, but properly written.