Split VirtualSensor callback.

A second callback is added responsible only for SensorDirectChannel
configuration changes.

Also, add a helper class for writing sensor events to the relevant
SensorDirectChannels.

Fix: 271345814
Test: atest VirtualSensorDirectChannelWriterTest
Change-Id: I5bfb3d6dfbb883d53dce9f72f747ae88eaf3228e
5 files changed