Monitor crashes of audio hal service via linkToDeath

Hwbinder 'linkToDeath' mechanism is used to track abrupt
disappearance of server hal objects due to hal server crash.

Upon hal server crash, notifications can be sent to binder
clients if needed, then the audioserver crashes itself as the
current audio HAL design does not provide an easy way to restore
all the transient objects (devices, streams, effects) in their
pre-crash state.

Bug: 34158778
Test: In binderized mode, kill audio hal server
Change-Id: If9265711edc445984601fcb5c29d2c173a370762