Add support to configure CI schedules

Rework the collection handling to make it more generic and handle both protected branches and CI schedules.

• Factor out set splitting in a reusable function
• Factor out applying changes to an object in a reusable function
• Replace printbranch() with a more generic printdict()
• Use dictionary access to handle protected branches
• Drop the ProtectedBranch dataclass
• Use the object delete() method for protected branches
• Use get_changes() to detect the changes to be applied
• Make collection handling generic
• Add support for scheduling CI triggers

A followup MR will actually add the rules to our ruleset, once the implementation is landed.