Support vX.Y floating tags for releases

[guicassolato]

Enhance the release workflow so it adds/moves a "vX.Y" tag whenever a "vX.Y.Z" version is released.

The name of the release branch should also be release-vX.Y instead of current release-vX.Y.Z. Whenever the release is a patch release (i.e. on top of an existing release-vX.Y branch), a new branch does not need to be created, but only the floating tag moved. Inversely, when the release is a new major or minor release, a new branch branch must be created, as well as the new corresponding floating tag.