Merge queue tracking issue

[Sakib25800]

• Add auto builds to PRs (Add PR auto build column #324)
• Delete attached auto build and cancel running workflows on PR push (Delete auto build on PR and cancel running workflows #326)
• Add merge queue skeleton - we introduce the merge queue and refresh event (Merge queue skeleton #350)
• Add auto build creation, merge to base branch (Merge queue #330)
• Add tests for PR#326 (Add auto build cancel tests #383)
• Update auto build docs (Update auto build diagram #385)
• Improve auto build error handling (Improve merge queue error handling  #386)
  • Reduce indentation and remove rightward drift (Reduce rightward drift in merge_queue.rs #405)
  • Deal with merge conflicts / non-fast-forward (Fast forward error handling #406)
  • Auto build startup failure (Improve auto build startup recovery #410)
  • Sanity checks (Add merge queue sanity checks #413)
• Mini-DSL for testing API?
  • Merge queue #330 (comment)

[Sakib25800]

@Kobzol, if you have anything further to add, feel free to suggest else we're finished with this issue.

[Kobzol]

I think that you did most/all of what I described in #386 (comment). I think that we might want to have a few more tests, and maybe some DSL for that, but that's not urgent. I will take a look at the current implementation holistically, and try to test it on the kindergarten repo, and maybe add a few more tests.

In the meantime, if you want to continue forward, then I think you can either work on improving the queue page (#371), implementing bors retry (#319), or start thinking about rollups! Let me know on Zulip if you want to brainstorm how rollups could be handled.