Add support for identifying a target release by release ID, not just tag name.

[vorporeal]

GitHub's release updating REST API uses the release ID as the key for determining which release to update. This action provides said ID as an output when creating a new release, but then doesn't let you use that ID to identify a release, leading to complexity when trying to update a draft release. (Additionally, it means that this action needs to filter down the entire list of releases by tag name, even though it has already provided callers with the necessary ID.)

Would be great if we were able to provide a release ID as an input, and if we do, that's used unconditionally instead of trying to compute release ID based on tag name.