Introduce HalVibratorHelper for tests

Move fake VibratorController test helper to new class that can provide
an HalVibrator implementation for testing, in preparation for new
implementation.

Extract VibratorController unit tests to run against HalVibrator
interface, so same tests can be reused by new implementation.

All tests were preserved by this change.

Bug: 421428555
Flag: android.os.vibrator.remove_hidl_support
Test: FrameworksVibratorServicesTests
Change-Id: I56afcb542aace24bbe95345bec9587cd10135150