Add flags to sync to customize behavior
Great idea from https://gitlab.com/gitlab-org/cli/-/issues/7473#note_1953388542
> One question, does `glab stack sync` support flags like `--assignee`, `--label` and `--reviewer`? In my team it is often the case that all branches in a stack are reviewed by the same person/people, so assigning these through the CLI would meaningfully streamline the process. If it is not yet possible, I would propose it as a possible future improvement
issue