Extract 'sync_code_owner_approval_rules' service

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Problem to solve

We added EE::ProtectedBranches::CreateService#sync_code_owner_approval_rules as part of moving code owners onto protected branches, but I think we can extract this logic into a new service class.

Proposal

We'll want this to be able to sync existing MRs after creating new approval rules https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/app/services/ee/protected_branches/create_service.rb#L25

Acceptance Criteria:

• This logic is contained in it's own service class