Move SDC to the theme system once its stable

Problem/Motivation

SDC has been added as an experimental module to Drupal 10.1.0. Once all of the stable blocking issues, SDC will be incorporated as part of the Drupal theme system.

Proposed resolution

Once all of the stable blocking issues in 🌱 Single Directory Components module roadmap: the path to beta and stable Active incorporate SDC as part of the theme system.

Remaining tasks

API changes

Release notes snippet