Add a mechanism for configuring the A2DP Source codecs

* Added a new class BluetoothCodecConfig that contains codec-related
  configuration or capabilities: codec type, priority, sample rate,
  bits per sample, channel mode, and codec specific fields.

* Extended the Bluetooth A2DP AIDL interface to get/set the current
  codec configuration

* Added new call handleBluetoothA2dpDeviceConfigChange() to the Media
  Framework that is called when there are changes in the
  Bluetooth A2DP device configuration - e.g., the A2DP codec is changed.

Test: A2DP streaming to headsets, TestPlans/71390
Bug: 30958229
Change-Id: I9a82716cbc2a5efbe77352a031ac80c88f6a2459