Rename protected_branches association
The following discussion from !157364 should be addressed:
- [ ] @vyaklushin started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/157364#note_1970271993): (+2 comments)
> Currently, `project.protected_branches` returns only protected branches for the project (without group-level protected branches). But for majority of validations we want to consider all possible protected branches (project + group level).
>
> As a option, we can try to migrate the code to use the following naming for associations. Something like:
>
> * `project.project_protected_branches`
> * `project.group_protected_branches`
> * `project.all_protected_branches`
>
> That should prevent developer from using `project.protected_branches` with an assumption that this method also considers group-level protected branches.
issue