Editor: Add block directory styles to script-loader

[ryelle]

This adds the block directory styles as a dependency of the edit-post style.

Fixed screenshot:

Trac ticket: https://core.trac.wordpress.org/ticket/50661

---

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

[TimothyBJacobs]

Do we need to remove the manual enqueues from edit-form-blocks.php.

[ryelle]

What's the reason for enqueueing in that file, instead of setting up dependencies in script-loader? If I were to follow the JS, I'd remove the dependency here, but I'm not sure which is the preferred method.

[TimothyBJacobs]

I'm not sure. Maybe @tellyworth knows?

[tellyworth]

It was just a silly oversight on my part while backporting, it wasn't intentional.

[ryelle]

I've moved the enqueue calls to new function, wp_enqueue_block_editor_assets_block_directory, hooked into enqueue_block_editor_assets, so script & style are both added together now.

This also provides a method for disabling the block directory, by unhooking that function:

add_action(
	'plugins_loaded',
	function() {
		remove_action( 'enqueue_block_editor_assets', 'wp_enqueue_block_editor_assets_block_directory' );
	}
);

See WordPress/gutenberg#23961

[desrosj]

This was committed in https://core.trac.wordpress.org/changeset/48537. For reference, I went with a different function name, wp_enqueue_editor_block_directory_assets(). It read a bit more clear to me.