libaudiohal: Allow late registration of HIDL HAL services

DevicesFactoryHalHidl registers a notification callback
with a service manager to get notified about registration
of new HAL services.

The specific code for the MSD HAL has been removed,
this HAL service is now handled using the added generic
mechanism.

Bug: 149854039
Test: make
Change-Id: I2f7f83dec11ac2390f674afd9e4451ef46dde04e
Merged-In: I2f7f83dec11ac2390f674afd9e4451ef46dde04e