psc: Move and refactor getUidRecord to ProcessRecordInternal

Move `getUidRecord()` from `ProcessRecord` to its superclass
`ProcessRecordInternal`. Update the method signature in
`ProcessRecordInternal` and its callers to return `UidRecordInternal`.
This change standardizes the use of the internal representation for
UidRecord across relevant internal components.

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

Change-Id: I9aafda0bc52b5a7f1339a3316842b35c0727d529