Release management: automatically tag @since annotations with the correct version #151

As of SCF 6.4, every time we add a new APi, we need to manually add the specific version @since annotation, which can lead to inaccuracies: if there is a new release before the branch with the new API is merged, its @since annotations need to be updated.

SCF should have a placeholder like {NEXT_MAJOR_VERSION} that gets replaced with the appropriate version during the release process jobs, so that contributors just need to type @since {NEXT_MAJOR_VERSION}.