Apply device config vibration scales for external vibrations

Apply scale factor sent by the ExternalVibratorService directly to the
haptic channels when the device config feature flag is enabled.

If no scale factor is provided this will fallback to the scaling V2 for
calculating the scale factor based on the scale level, for consistency.

Bug: 427503922
Test: ExternalVibrationUtilsTest
Flag: android.os.vibrator.vibration_scale_device_config_enabled
Change-Id: Id4f719830adc6444e7a0387ebd8459f274f47b0a