Patterns: provide a way to opt-out of Gutenberg patterns and core patterns updates

[ramonjd]

Description

This PR is a proof of concept (POC) to test a feature proposal.

This PR provides filters to opt out of:

1. removing core patterns, in case Gutenberg users want to use Core patterns
2. adding Gutenberg patterns
3. loading core patterns from remote source

See the issue for more context: #31922

How has this been tested?

By default all Gutenberg patterns should be available in the inserter.

To test the filters add the following block to the end of lib/init.php

/* TEST CODE START - DELETE ME */

function should_register_gutenberg_patterns() {
	return false;
}
add_filter( 'register_gutenberg_patterns', 'should_register_gutenberg_patterns' );

function should_remove_core_patterns() {
	return false;
}
add_filter( 'remove_core_patterns', 'should_remove_core_patterns' );

function should_load_remote_patterns() {
	return false;
}
add_filter( 'load_remote_patterns', 'should_load_remote_patterns' );

/* TEST CODE END - DELETE ME */

Returning false from should_register_gutenberg_patterns() should remove Gutenberg patterns.

With Gutenberg patterns	Without

Returning false from should_update_core_patterns() should not replace/update core patterns

With updated core patterns	Without updated core patterns

Types of changes

Non-breaking additional functionality.

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[ramonjd]

Closing this for now as it's a bit stale and there might be more profitable ways of doing this independent of Gutenberg now that 5.8 is released.