doc: clarify options for single customization hooks thread
triggered by comment on #47747. This PR adds clarification on single customization chain thread that were introduced with #52706
@nodejs/loaders
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
triggered by comment on #47747. This PR adds clarification on single customization chain thread that were introduced with #52706
@nodejs/loaders