SF: Add test for emitting of mode change event

Also, remove the trivial SchedulerTest.dispatchCachedReportedMode, and
clean up related tests.

Bug: 255635821
Flag: TEST_ONLY
Test: SchedulerTest.emitModeChangeEvent
Change-Id: Id380776438d93f701f27fc5887e9b99064d32d0e
2 files changed