[Meta] Tasks to deprecate Stable

Problem/Motivation

This issue is to coordinate and track the steps needed to deprecate Stable so it can be removed from core. See Remove a core module and move it to a contributed project of the deprecation policy.

Proposed resolution

Remaining tasks

1. ✅ Create the contrib project, Stable, with a stable release. See the deprecation policy for the git commands. project/stable
2. ✅Convert integrations.
   • #3308987: Remove references to Stable
   • Move Help Topics to the extensions.
   • Possible issue for removing references to the extensions from database dumps.
   • Possible issue for moving theme-specific integration to the theme.
   • Possible issue for updating Update path tests. See Writing Automated Update Tests for Drupal 8 (or later) for details.
   • Possible issue for removing templates from the extension’s markup.
   • Do a thorough search of core for any remaining references to the extension. If references are found, outside of the extension, then create issues to remove the references.
3. ✅Deprecate the core Stable theme, #3308890: Deprecate Stable theme
   1. Create a section on Deprecated and obsolete themes and
      themes to provide recommendations for sites using theme Stable. The recommendation are to include
      instructions for sites using Stable and for contributed themes that depend on Stable.
   2. Set lifecycle to deprecated.
   3. Set lifecylcle_link to the section added above, https://www.drupal.org/node/3223395#s-stable.
   4. The change record for this issue includes a link to the doc page.

User interface changes

API changes

Data model changes

Release notes snippet