Remove unused ProcessStateRecord#mHasProcStateChanged field

The `mHasProcStateChanged` field in `ProcessStateRecord` and its
corresponding setter/getter methods are no longer in use. This patch
removes the field and all references to it to clean up the code.

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

Change-Id: Ib300a16a89844cb86dee47e035468bfb2e83165f