Cache `branch_requires_code_owner_approval?`

This saves a few queries during the MR index listing

Changelog: performance
EE: true

ee/app/models/concerns/ee/protected_branch.rb

@@ -16,7 +16,8 @@ module EE
       def branch_requires_code_owner_approval?(project, branch_name)
         return false unless project.code_owner_approval_required_available?
 
-        project.protected_branches.requiring_code_owner_approval.matching(branch_name).any?
+        ::Gitlab::SafeRequestStore["project-#{project.id}-branch-#{branch_name}".to_sym] ||=
+          project.protected_branches.requiring_code_owner_approval.matching(branch_name).any?
       end
     end