LKL-2162 Add setup-uv self-updating action

[mkirkeng-leukeleu]

Added workflow to sync this fork with the upstream repo once per day. This also pulls in all tags so we can use this action like any other: uses: leukeleu/setup-uv@v6.

We will need a PAT in the repository secrets (called SYNC_FORK_TOKEN for now) with read/write permissions for the contents of this repo and read/write for workflows as well (because workflows might be updated on the upstream repo and when we pull those in they will be changed here as well).

Edit: I did also test dependabot and it will happily open PRs to update the version of our forked action.

[153957]

🤔 If we merge this this action will run, but wont it then automatically remove itself? Perhaps I am missing how this is prevented? Should it sync and then rebase the commit which adds this action on the top?
Since these commits do not exist on the remote they would be removed when updating the sync (or the update would be blocked since it would be considered force pushing).

[mkirkeng-leukeleu]

🤔 If we merge this this action will run, but wont it then automatically remove itself? Perhaps I am missing how this is prevented? Should it sync and then rebase the commit which adds this action on the top? Since these commits do not exist on the remote they would be removed when updating the sync (or the update would be blocked since it would be considered force pushing).

Since we really only care about tags (that's what we refer to in other repos and what will be used to actually run the action there) this action only fetches tags and pushes those but doesn't actually update the main branch in this repo.