Tasks to deprecate Migrate Drupal

Problem/Motivation

Track the steps needed to deprecate extension Migrate Drupal. See Remove a core module and move it to a contributed project of the deprecation policy.

The removal of extension Migrate Drupal was approved in #3371229: [Policy] Migrate Drupal and Migrate Drupal UI after Drupal 7 EOL. It is happen after Drupal 7 is EOL.

Remaining tasks

1. Move integrations implemented by other modules to the extension.
   Create child issues or child meta issues, as needed, to address the following points. Not all points will apply to all extensions.
   • Deprecate source plugins for legacy Drupal. Deprecate DrupalSqlBase. This should cover all the source plugins for legacy version.
   • Deprecate MigrateField plugins
   • Decide which Migrate Destination plugins to deprecate.
   • Decide which Migrate Process plugin, in other modules, to deprecate.
2. 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. Create a section on Deprecated and obsolete modules and themes to provide recommendations for sites using extension EXTENSION_NAME. The recommendations are to include instructions for sites using the extension and for contributed projects that depend on then extension.
4. Add the following to the extension info.yml file

lifecycle: deprecated
lifecycle_link: https://www.drupal.org/node/3223395#s-EXTENSION

5. Add @group legacy to all tests in the extension.
6. Add a change record and include a link the the doc page.
7. Deprecate any library that is only used by the extension.