[meta] auto-merge triggering too early due to skipped pull_request check

[shiftinv]

Pushing to an internal PR naturally triggers all checks that run on push and pull_request events.
Like the other jobs, the check job gets skipped on the pull_request trigger for internal PRs, since the push event already runs the same stuff.

Since the check (push) job depends on other jobs and doesn't run (or even get queued) until they're finished, and the check (pull_request) job gets skipped, there's a window where the requirements set in the branch protection rules are fulfilled (as skipped checks are valid) and the PR gets merged even though some jobs aren't finished yet.

For example, this pytest job finished at 13:32:34, while the PR had already been merged at 13:32:16.

[onerandomusername]

It looks like if we change some of our workflows and tighten them up a bit as shown here we should solve the issue, since it would cancel the workflow instead of skipping it.

[shiftinv]

Moved the unresolved part of this issue to a new one, #937.