1/n: Update BiometricDialog (SystemUI side) with cleaner lifecycle

1) Clean up BiometricDialogImpl. As a side-effect of 2, which cleans up
   the dialog lifecycle, we no longer need to have a handler here. This
   greatly simplifies the code here.
2) Clean up interface between BiometricDialogImpl and the UI
   (BiometricDialogView).
3) Clean up interface between BimetricService and BiometricDialogImpl.
   SystemUI is now responsible for dismissing the dialog.

Test: atest BiometricDialogImplTest
Bug: 138628043

Change-Id: Ic1fea4c05c27dfc7eb6fc661f517f0380b9fff99