Site Editor: Augment template details panels

[jameskoster]

Related: #50386

Template detail panels in the Site Editor include a description of the template:

We can make these panels more useful. Some considerations:

• List template parts within the template, a way to contextually switch them, and potentially cross-link to their detail panels.
• Note the original author / theme, and last editor.
• Offer a way to edit settings such as:
  • "Posts per page" for archive templates.
  • What front-page should display (latest posts or a static page).
• Include quick links:
  • Revisions
  • Reset / delete / duplicate, and other actions.
  • Explore associated patterns (loaded from the directory, installed themes, etc).

[richtabor]

Let's close this in favor of the existing #49597 issue. It's been updated to focus on template details for blog (index and home) and category template. 🚀