Editor: Update REST API preloaded paths for 6.8

[Mamaduka]

Combines the following core sync PRs: #7687 and #7695.

Gutenberg PRs:

• Site Editor: preload settings requests gutenberg#66488
• Preload: fix e2e test gutenberg#67497
• Site editor: preload post if needed gutenberg#66631
• Preload: parse post ID from p (path) gutenberg#67465
• Site Editor: speed up load by preloading home and front-page templates gutenberg#66579
• Site Editor: Pages: Preload template lookup gutenberg#66654
• [mini] Preload: add post type gutenberg#67518
• Site Editor: Fix template lookup preloading for non-draft pages gutenberg#69400
• Editor: Preload template lookup gutenberg#69454

Trac ticket: https://core.trac.wordpress.org/ticket/63050

---

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.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

Core Committers: Use this line as a base for the props when committing in SVN:

Props mamaduka, joemcgill, peterwilsoncc.

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[github-actions]

Test using WordPress Playground

The changes in this pull request can previewed and tested using a WordPress Playground instance.

WordPress Playground is an experimental project that creates a full WordPress instance entirely within the browser.

Some things to be aware of

• The Plugin and Theme Directories cannot be accessed within Playground.
• All changes will be lost when closing a tab with a Playground instance.
• All changes will be lost when refreshing the page.
• A fresh instance is created each time the link below is clicked.
• Every time this pull request is updated, a new ZIP file containing all changes is created. If changes are not reflected in the Playground instance,
  it's possible that the most recent build failed, or has not completed. Check the list of workflow runs to be sure.

For more details about these limitations and more, check out the Limitations page in the WordPress Playground documentation.

Test this pull request with WordPress Playground.

[joemcgill]

@Mamaduka Left a few comments, but overall this looks right to me. Did a very quick performance check and can confirm that this seems to speed up the initial render of the site editor.

[joemcgill]

In #7695, these were only preloaded if not in the post context. Is the intention to load them always?

[peterwilsoncc]

@peterwilsoncc, what would be the best way to address it in post _wp_get_site_editor_redirection_url?

Sorry mate, I am a little unclear what you are asking here? Is it regarding the backport of the code you have left out for now? Presuming that's the case, I think it will need to be much the same code as both of the following URLs can be used for editing a page with the ID 2:

• http://wp-dev.local/wp/wp-admin/site-editor.php?canvas=edit&p=%2Fpage%2F2
• http://wp-dev.local/wp/wp-admin/site-editor.php?p=%2Fpage&postId=2&canvas=edit

The latter is used in the site editor.

[Mamaduka]

Is it regarding the backport of the code you have left out for now?

Sorry, @peterwilsoncc, that was the question.

[Mamaduka]

This should be ready for final review.

[Mamaduka]

See: WordPress/gutenberg#69400.

[Mamaduka]

Removed default_template_part_areas and default_template_types query arguments for index prealoding path.