psc: Extract ServiceRecordInternal

This change refactors ServiceRecord to extend ServiceRecordInternal, an
abstract base class that centralizes common service state fields used by
OomAdjuster.

This is a pure refactoring and introduces no behavioral changes.

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

Change-Id: I1058a89141ecad9b3bd6f911247fb7b9adac59f7