[ci] Add auto-updating last-successful branch

[driazati]

This adds a script that runs on a cron to discover the last commit where CI all passed (every job was successful and tvm-ci/branch is included) and updates a git branch last-successful that tracks this commit from main. This can be used for checking out the latest unbroken TVM, which can be useful for developers wanting a good changeset to base their changes on or for infra needing a clean, up-to-date TVM.

Also soliciting better names than green

[Mousius]

I suggest last-successful as a tag so we're not coupled to the colour 😸

[areusch]

one problem here is that a tag doesn't automatically update with git fetch. A branch would. it's a little confusing to have a branch instead of a tag, but a branch is confined to origin/ namespace and will auto-update with git fetch. i think we should switch to updating a branch to avoid confusing behavior where last-successful is not updated after a fetch.

cc @leandron @mbrookhart if there are other ideas

[github-actions]

It has been a while since this PR was updated, @leandron @mbrookhart @AndrewZhaoLuo @driazati @areusch please leave a review or address the outstanding comments

[Mousius]

This looks ready to me, @areusch can you take another look?

[github-actions]

It has been a while since this PR was updated, @leandron @mbrookhart @Mousius @AndrewZhaoLuo @driazati @areusch please leave a review or address the outstanding comments

[driazati]

Sorry about the overactive bot everyone, it's still missing some checks to look at before sending out these pings

[Mousius]

Let's get this in so we can start iterating if we need to 😸

[fpedd]

What happened to this branch? The CI job got manually disabled about 5 months ago, it seems.

[driazati]

I filed an issue with the reason for disabling and potential fix: #14618