Guard Branch Rule Editing with permissions

So far, all editing options added to Branch Rule details page are hidden behind the edit_branch_rules feature flag, but they are not guarded by permissions.

Since we are combining a couple of settings on one page, it's essential that we guard each editing option with permissions present in the currently available settings.

UI element to guard	code implementation	already existing permission
Delete rule	/branch_rules/components/view/index.vue#L279	https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/views/projects/settings/repository/\_protected_branches.html.haml?ref_type=heads#L1
Rule target	/branch_rules/components/view/index.vue#L300	https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/views/projects/settings/repository/\_protected_branches.html.haml?ref_type=heads#L1
Allowed to merge	/branch_rules/components/view/index.vue#L349 /branch_rules/components/view/protection.vue#L51	https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/views/projects/settings/repository/\\\_protected_branches.html.haml?ref_type=heads#L1 guard added in !165192 (merged)
Allowed to push and merge	/branch_rules/components/view/index.vue#L349 /branch_rules/components/view/protection.vue#L51	https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/views/projects/settings/repository/\_protected_branches.html.haml?ref_type=heads#L1 guard added in !165192 (merged)
Allow force push and Requires code owner approval	!153281 (68bc7cc7)	_protected_branch.html.haml#L2 Code owner approval required: https://gitlab.com/gitlab-org/gitlab/-/blob/71d42c048c56ec6a4962b8e94543ac6faa5e1472/ee/app/views/protected_branches/ee/\\\\\\\_code_owner_approval_table_head.html.haml#L1 https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/views/projects/settings/repository/\\\_protected_branches.html.haml?ref_type=heads#L1 guard added in !165192 (merged)
Merge request approvals	/branch_rules/components/view/index.vue#L406 approval_rules_app.vue#L103	projects_helper.rb#L62
Status checks	/branch_rules/components/view/index.vue#L349 /branch_rules/components/view/protection.vue#L51	no permissions in place, we only make sure this licensed feature is available