vibrator: add CAP_EXTERNAL_AMPLITUDE_CONTROL

For HIDL, vibrator may change the value of supportsAmplitudeControl
based on context. Since the interface is being redone in AIDL, we're
avoiding this changing value and providing capabilities for amplitudes
we expect to be available in different states.

Bug: 141828236
Test: VtsHalVibratorTargetTest
Change-Id: Idf0b28ffe5b1175469d32e790b10b4232482dc2b