Idempotent release action (#2353)

* Do not require the released commit to be at the tip of the branch.

* Update comment.

* If you release an old commit, it must be ready to go as is.

* Tag the commit that updates gradle.properties.

* Check out the specific commit instead of the branch.

* Simplify.

* We need to set the release branch.

* You can't refer to outputs directly.

* Make sure to tag the right commit.

* Pass the commit SHA explicitly.