psc: ConnectionRecordInternal accesses ServiceRecordInternal

Previously, `ConnectionRecordInternal` exposed specific service
properties (e.g., `lastActivityTimeMillis`, `serviceInstanceName`)
through dedicated getter methods. This CL removes these redundant
getters and provides a `getService()` method, returning the
`ServiceRecordInternal` instance.

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

Change-Id: I7944805e2f39a3cb32ffd9bd349174e24bc15143