[CDM] Add CompanionExemptionProcessor

1. Auto revoke exemption now checks if there's any association for the package.
2. Power saver exemption now checks if there's any connected device for the
   package.
3. TODO: CompanionAppBinder.onPackageChanged shouldn't invalidate the
   whole user registry, it should rather remove the package only. I will
   do it in a separate CL.

Bug: 373957005
Test: manually tested 3 exemptions
Flag: EXEMPT bugfix
Change-Id: I8e3a6099c3e09b0bdb22844e9a57c415f6179f46