Move DTT repo to drupal.org

After a tremendous amount of flailing around by jonathanjfshaw and then myself, what finally worked to get DTT back to ✅ (was failing for months) AND switched to use the official drupal gitlab_templates was to move the project to drupal.org. Something changed with the gitlab.com CI runners and we aren't smart or knowledgeable enough to adapt.

You can see the new DTT repo and its green PR at https://git.drupalcode.org/project/dtt/-/merge_requests/1/pipelines. Its unannounced and just just a proof of concept for now.

I think this is a good time to move DTT to drupal.org. I dislike d.o. issues and even when those are moved to Gitlab, they will still use the very-much-invented-here "issue fork" workflow. Sigh. Thankfully this project doesn't use issues much. And maybe d.o. will let projects opt out of issue forks?

I'd love input on how to transition smoothly. Here is a quick checklist that I will keep up to date:

• Edit our Packagist project so that it points at drupal.org. The namespace won't change.
• Add an integration/webhook on drupal.org Gitlab
• Open an equivalent merge request on d.o. for each open merge request here. Add links back and forth so folks can read the prior discussion
• Add a link in the README to the all existing issues and the closed MRs. Leave them behind in old repo.
• Archive this repo
• Configure the drupal.org project.
• Announce the move on Twitter and Slack #testing

What do folks think about this proposal? I'm open to positive or negative feedback.

/cc @jibran @hestenet-drupal @drumm @jonathanjfshaw @mstrelan @acbramley @larowlan @fjgarlin