add native IPlayer interface implementation

Generalized the IPlayer implementation done for OpenSL ES
so that it can be used by other native audio players
Created two classes:
 - PlayerBase implementing the interfacin native AudioManager and
 IPlayer methods
 - TrackPlayerBase, a derived class specialized for AudioTrack.

Bug: 62027849
Test: verify regressions with OpenSL ES buffer queue player

Change-Id: If5ad21a3c1a243fba0b312001c5034102e6d6672