prevent_pushing_and_force_pushing should reflect in branch rule UI

Why are we doing this work

When an MR approval policy sets approval_settings.prevent_pushing_and_force_pushing, we reflect its effects in the protected branch settings UI. But since prevent_pushing_and_force_pushing predates the branch rules feature set, this isn't the case for the branch rule settings UI (Settings > Repository > Branch rules).

For example, the branch rules UI may confusingly note Allowed to push and merge: Maintainers for a rule, since prevent_pushing_and_force_pushing isn't accounted for.

Relevant links

• https://gitlab.com/gitlab-com/request-for-help/-/issues/2602

Non-functional requirements

• Documentation:
• Feature flag:
• Performance:
• Testing:

Implementation plan

TBD

Verification steps

TBD