Editor: Preload the entity fields and actions the editors read

[jorgefilipecosta]

Backports the preloads of WordPress/gutenberg#85081 (post editor entity fields) and WordPress/gutenberg#85155 (site editor entity actions).

The editors read the fields and actions of the post types they show from /wp/v2/entity-fields and /wp/v2/entity-actions. Core preloads the fields in the site editor and the actions in the post editor, but not the other way around.

This PR:

• Makes _wp_preload_entity_fields() also preload the fields of the edited post type in the post editor, which the post summary of its inspector reads since Editor: Stabilize the DataForm-based inspector gutenberg#85081.
• Makes _wp_preload_entity_actions() also preload, in the site editor, the actions of the edited post and of the post types its screen lists (pages, templates, patterns and template parts), reusing _wp_get_site_editor_screen_post_types().
• Replaces the test that asserted the post editor does not preload the fields, and covers the site editor actions per screen.

The new requests only happen once Core's Gutenberg pin includes the code that reads both routes. Until then the preloads go unused, as the existing ones do.

Testing Instructions

1. With a Gutenberg pin that includes Editor: Stabilize the DataForm-based inspector gutenberg#85081, open a page in the post editor and verify no /wp/v2/entity-fields?kind=postType&name=page request is made.
2. Open wp-admin/site-editor.php?p=%2Fpage and verify no /wp/v2/entity-actions?kind=postType&name=page request is made. Do the same on ?p=%2Ftemplate (wp_template) and ?p=%2Fpattern (wp_block and wp_template_part).
3. Run npm run test:php -- --group entity-fields,entity-actions.

Trac ticket: https://core.trac.wordpress.org/ticket/66343

Use of AI Tools

AI assistance: Yes
Used for: writing the code and the tests, and drafting this description; reviewed and edited by me.

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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.

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