libauiohal: Implement StreamOut callbacks

Implement StreamOutHalInterface::set{|Event|LatencyMode}Callback
methods. Due to differences in callback registration between
HIDL and AIDL, some extra management logic is required.

Bug: 205884982
Test: start cuttlefish with AIDL HAL enabled
      (there are no unit tests for these callbacks,
       and cuttlefish does not support offload)
Change-Id: Ic8e2ab5a0b75d1501289474b3064e5ca74f0e024