Implement a STHAL watchdog

This ensure that any soundtrigger HAL calls don't block the
soundtrigger middleware service for an excessive time.
The HAL process will be rebooted if that ever happens.

Change-Id: I649d04df93a2bcbb8d8818a820d22067a92a2d71
Fixes: 158863507
Test: Verified basic operation is maintained.
      Introduced an artificial HAL hang and verified that the HAL
      gets rebooted and normal functionality is restored.