[llvm] Reland pr code format updates (PR #71131)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

A bit more hacking:
* Apparently it's not as easy as I thought to check the mergability of a PR. It needs to be done through a separate API request specifically for that PR as the `pull_request.mergeable` field/associated fields are not populated in the CI run.
* Weird behavior exists. For example, you can still fetch the merge ref of a PR that has conflicts, it's just the merge ref for the last version of the PR that didn't have any conflicts (from what I can tell). Failing on mergeability fixes this issue though.

This PR should be in a landable state, acknowledging the lack of functionality in the case where there are merge conflicts. I've kept the `changed-files` step after the checkout to hopefully avoid an additional API call. If that still causes issues (there are still occasional transient failures not even related to fetch depth issues) and we're running out of API requests, we can also switch to the llvm bot token given this uses `pull_request_target`.



https://github.com/llvm/llvm-project/pull/71131