Block Patterns: Add block pattern plugins

[costdev]

This adds the following plugins, originally from the dotorg pattern directory repository:

Must-Use Plugins

• Locales: Defines locales used by GlotPress.
  • This may not be strictly necessary with GlotPress installed. However, I'm erring on the side of caution here by including it as dotorg's repo does.
• Locale Switcher: For switching locales.

Plugins

• Pattern Directory: Creates a directory to manage block patterns.
  • Defines the various post types, taxonomies, and rest fields, among other things, used in the Pattern Directory.
• Pattern Translations: Imports pattern translations into GlotPress and provides translated patterns.

This also includes several changes:

• Locales: Define $root_slug property.
  • This was throwing deprecation notices.
• Locales: Fix encoding on native name.
  • The native names were borked. Possibly an issue with how I retrieved them in the first place.
• REST: Use post meta, not user meta, for the author's data.
  • Since the authors won't be users on our server.
  • Note: This relies upon importing the author_meta key of the response to the author_meta post meta key.
• Patterns: Use a constant for the patterns URL
  • Previously a hardcoded dotorg URL, which is now a fallback if the constant isn't defined.