liboboe: initial checkin of core and legacy files.

Oboe C++ files that calls AudioTrack and AudioRecord.
Main C API implemented by src/core/OboeAudio.cpp

Test: gunit tests for the Legacy mode and handle tracker in tests folder
Bug: 33347409
Change-Id: I50f9fd99377efbd8de6fef1601e9af4c22c6ab46
Signed-off-by: Phil Burk <philburk@google.com>