psc: ProcessRecord extends ProcessRecordInternal

This renames ProcessStateRecord to ProcessRecordInternal, and refactors
ProcessRecord to directly inherit from ProcessRecordInternal, removing
the 'mState' member field. This change also removes the
ProcessRecordReader interface as its methods are now directly
implemented by ProcessRecord.

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

Change-Id: Ifad186ba1d0871b71decabb2faa9978ac0ffe22e