Use USAGE_IME_FEEDBACK in VibrationSettings#shouldVibrateForUserSetting

Fix a refactoring bug that in VibrationSettings#shouldVibrateForUserSetting
that we missed to re-calcuate the keyboard intensity to be
VIBRATION_INTENSITY_OFF when the user turned off the keyboard vibration
setting.

Also fix the unit test assertion in VibrationSettingsTest for testing
shouldIgnoreVibration() behavior when keyboard vibration setting on/off

Also remove mKeyboardVibrationOn from VibrationSettings, since now the
keyboard vibration intensity is now reflecting the current vibration
usage (USAGE_IME_FEEDBACK) without using this adhoc flag.

Flag: EXEMPT refactor
Bug: 358019438
Test: atest VibrationSettingsTest
Change-Id: I6ca03a58bef2d399e4afb55b4afd9958b4312d4a