am: Remove unused UidRecord fields

Remove unused mCurAdj, mSetAdj, and mNumProcs fields from UidRecord.
These fields were no longer in use, simplifying the class.

Bug: 425766486
Test: m services.core
Test: atest MockingOomAdjusterTests OomAdjusterTests
Test: FrameworksServicesTestsRavenwood_ProcessStateController
Flag: EXEMPT pure refactor

Change-Id: I0114a499cdcb628bc9df88baa2a56a010903c6a6