Use app uids in DndRule proto pulled atom

Rules created by the system ("android") have uid=1000 and apps have
their own unique uids.

Cached uids are removed when the automatic rule is removed.
 - ConditionProviders removes automatic rule on package removal
 - NotificationAccessDetails + NotificationAccessPreferenceController +
 ZenAccessController remove automatic rules on permission changes

Test: atest ZenModeHelperTest
Fixes: 158647401
Change-Id: I100490c4e4cd823a7f12faa518fbc4c2a172a9f7