VRR: Use appId to replace uid mapping

Uid is combination of user id and app id. Because the allowlist
is recored by pkg for each users. We could ignore the user id part
and it also could solve the issue we didn't update the mapping
when user added case.

Bug: 298722189
Test: atest SmallAreaDetectionAllowMappingsTest
Test: atest SmallAreaDetectionControllerTest
Test: Add new user and open Youtube short to check refresh rate
Change-Id: Ic80be38ebc19938bc061bf6121c68efc4ff9ac4c