Seperate responsibilities between (Branch|Tag)PushService and and Git::(Branch|Tag)HooksService

In gitlab-foss!31653 (comment 202209839) @DouweM identified that the line separating the responsibilities of the (Branch|Tag)PushService and the Git::(Branch|Tag)HooksService is quite blurry.

We should probably clean that up a little bit.

After gitlab-foss!31653 (merged) and gitlab-foss!31641 (merged) are merged, I believe the tree would look roughly like this:

• PostReceive#process_project_changes
  • post_received.project.repository.expire_branches_cache if post_received.includes_branches? (cache expiry)
  • post_received.project.repository.expire_caches_for_tags if post_received.includes_tags? (cache expiry)
  • changes.each
    • BranchPushService#execute
      • enqueue_update_mrs (async side effect)
      • enqueue_detect_repository_languages (async side effect`
      • execute_related_hooks (Git::BranchHooksService#execute)
        • execute_branch_hooks
          • Repository#after_push_commit(branch_name) (cache expiry, event tracking)
          • branch_(create|update|change|remove)_hooks (cache expiry: some no-op, event tracking, side effects)
          • Git::BaseHooksService#execute
            • repository.after_create (cache expiry)
            • create_events (side effect)
            • create_pipelines (side effect)
            • execute_project_hooks (side effect)
            • enqueue_invalidate_cache (cache invalidation, but requires list of commits)
            • update_remote_mirrors (side effect)
    • TagPushService#execute
      • Repository#before_tag_push (event tracking)
      • Git::TagHooksService#execute -> Git::BaseHooksService
        • repository.after_create (cache expiry)
        • create_events (side effect)
        • create_pipelines (side effect)
        • execute_project_hooks (side effect)
        • enqueue_invalidate_cache (cache invalidation, but requires list of commits)
        • update_remote_mirrors (side effect)
  • PostReceive#after_project_changes_hooks

I think we should add all cache expiry calls that relate to 1 tag or branch into the PushService, while all side effects that require loading commits and so on into the hooks.

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The following discussion from gitlab-foss!31653 (merged) should be addressed:

• @reprazent started a discussion: (+6 comments)

  Even though we're not invalidating caches in the BranchPushService anymore, I think we should call the BranchPushService#execute_related_hooks before enqueuing anything else.

  We know now that there's nothing else in the Repository#after_create_branch and Repository#after_remove_branch, but that could change, and we're also handling the Repository#after_create in the hooks. So I think we have to assume that everything scheduled expects the hooks to have run.