Changes to VibrationThread in preparation for sessions

- Make session end method async, to follow the vibration thread
  cancelation structure.
- Remove service callback for vibration complete, make thread notify the
  conductor directly.
- Simplify vibration reporting to be triggered only when the thread
  reports the vibration cleanup is complete, remove boolean param.
- Move IBinder link/unlink to death from the thread to the service, as
  sessions will be linked there as well.

Bug: 345414356
Flag: EXEMPT refactor
Test: FrameworksVibratorServicesTests
Change-Id: I2358ec00cbee8569e9a0bce2f0b284d41a3405ae