SFPS indicator and BiometricPrompt MVVM cleanup

Removing stale iconOverlayView references (layout files,
BiometricViewSizeBinder). Also cleans up MVVM structure by moving
dependencies to SideFpsOverlayViewModel and new interactor rather than
SideFpsOverlayViewBinder and updates PromptIconViewModel to access
dependencies directly from parent PromptViewModel instead of passing
them in directly. Moves shared test setup functions to
BiometricTestExtensions.

Flag: EXEMPT cleanup
Fixes: 364937003
Bug: 288173662
Test: atest SideFpsOverlayViewModelTest
Test: atest SideFpsOverlayInteractorTest
Test: atest SideFpsOverlayViewBinderTest
Test: atest PromptViewModelTest
Change-Id: I2bde7a83bc2c5eb626d2a7dfa2f4fb85dede68f9