am: Migrate updateAndTrimProcessLSP() to ProcessRecordInternal

This CL updates OomAdjuster's updateAndTrimProcessLSP to use
ProcessRecordInternal. To achieve this, some fields and
methods previously part of ProcessRecord are moved to the
ProcessRecordInternal abstract class.

Bug: 441412109
Test: m services.core
Test: atest MockingOomAdjusterTests OomAdjusterTests
Test: atest FrameworksServicesTestsRavenwood_ProcessStateController
Flag: EXEMPT PURE_REFACTOR

Change-Id: I64ba65029621b34b16172b198d0585bd2e89b3e8