psc: UidRecordInternal manages ProcessRecordInternal directly

This change renames UidStateRecord to UidRecordInternal, and moves
process management methods (addProcess, removeProcess,
getProcessRecordByIndex) from UidRecord to UidRecordInternal. This allows
UidRecordInternal to directly manage ProcessRecordInternal instances,
improving abstraction within the Process State Controller (PSC).

UidRecord now overrides these methods, casting to ProcessRecord
where necessary, as it holds specific ProcessRecord objects.

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

Change-Id: I555afda45c9770835d3ae290b3697dbb4549651d