psc: Extract ConnectionRecord flags/ongoing calls to internal class

Moves `mFlags` and `mOngoingCalls` fields, along with their accessor
methods from `ConnectionRecord` to a new abstract base class,
`ConnectionRecordInternal`, in the `psc` package.

`ConnectionRecord` now extends `ConnectionRecordInternal` to inherit
these common attributes and methods, preparing for future refactoring
related to process state controller.

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

Change-Id: If1aac17a0d5251bfb7d8d90ff8d8dd11c95146a6