vibrator: aidl: Apply Compose API Feedback

- Make Thud and Spin optional due to complexity.
- Make "scale" inclusive of zero, which represents minimum "feelable"
  intensity.
- Update VTS tests appropriately.
- Fix typo in VTS test names.

Bug: 151084263
Test: VTS on Flame, Walleye, and Cuttlefish
Signed-off-by: Harpreet \"Eli\" Sangha <eliptus@google.com>
Change-Id: Ib0d046be83ee79ab38e0b9c3fb87a41f23879f8b