Editor: Preload REST requests the post editor fetches on mount

[ellatrix]

See ​https://github.com/WordPress/wordpress-develop/pull/11948

## What?

Adds four entries to $preload_paths in wp-admin/edit-form-blocks.php:

• /wp/v2/templates/lookup?slug=front-page: homepage actions (getDefaultTemplateId)
• /wp/v2/taxonomies?context=edit: taxonomies panel
• OPTIONS on the current post-type collection: canUser permission probe
• /wp/v2/users/{author}?context=view&_fields=id,name: post-author display name

## Why?

The post editor fetches all four on first mount. Preloading them serves the data from the inline cache and removes network round-trips from the boot path. Unbounded per_page=-1 queries (comments, wp_pattern_category) are deliberately not preloaded.

## Gutenberg counterpart

​https://github.com/WordPress/gutenberg/pull/78565

## Trac ticket

https://core.trac.wordpress.org/ticket/65636

## Testing

Gutenberg's preload spec (test/e2e/specs/preload/post-editor.spec.js) asserts these URLs no longer fire as post-mount network requests.

[ellatrix]

In 62749:

Editor: Preload REST API requests fetched on editor load.

Add four entries to the block editor preload paths in wp-admin/edit-form-blocks.php: the front-page template lookup, the taxonomies list, the OPTIONS permissions request for the post type collection, and, for post types that support it, the post author's display name. The editor previously requested all of these over the network on first load.

Developed in ​https://github.com/WordPress/wordpress-develop/pull/11948.

Props ellatrix, mamaduka.
Fixes #65636.