Support backporting onto a ongoing release branch #6028
Description
Is your feature request related to a problem? Please describe.
When a fix is required to unblock an ongoing release process (on branch release-X.Y.Z) there is currently no label to support backporting changes there.
Instead one would have to either cancel the release process and re-fork from stable/X.Y or manually duplicate the commits.
Describe the solution you'd like
The release workflow should create an associated backport label after the release- branch has been forked off and delete that label as soon as it is no longer relevant.
Describe alternatives you've considered
We could keep the current flow