Update sample code and documentation to use new data and error callback interfaces

[dturner]

This PR refactors the sample code away from using a single callback (AudioStreamCallback) for both data and error events to using the new AudioStreamDataCallback and AudioStreamErrorCallback classes.

The only issue I faced was that the original DefaultAudioStreamCallback (used by hello-oboe and megadrone) would attempt to set thread affinity inside the data callback and would reset it inside the error callback through a single field: mIsThreadAffinitySet.

By separating the two callbacks the error callback no longer has access to this field. To solve this I added a reset method to DefaultDataCallback which can be called to reset the data callback to its initial configuration (in this case, only the thread affinity).

The responsibility for calling reset moves away from the error callback, which just calls restart on its IRestartable parent. It's up to the parent to call reset on the data callback. Example here: https://github.com/google/oboe/compare/master...dturner:split_callbacks?expand=1#diff-300176f2b98467e0664a62ca6d40aa3f5c2401121741bcdea15a787557a6071bR133.

[philburk]

We will coerce the ErrorTimeout to ErrorDisconnect in Oboe.