This changes the FetchRelease implementation to look up draft releases directly using by its pending tag name, as opposed to resorting to the Releases list API which is backed by Elastic Search and thus suffers replication lag after the creation of a draft release.
Bonus: all release lookup functions now accept a context for cancellation.
When using GITHUB_TOKEN in Actions, the permissions on a repository are
null and therefore we can't check whether the viewer has push access or
not. The solution is to unconditionally check for draft releases instead
of trying to be smart about it. Draft releases are going to be on top,
so we don't have to paginate through all releases in a repository.
