audio_hal_interface: Provide the preferred encoding interval

Adds the dataIntervalUs to the pcmConfig used for a2dp software
path. This value will inform the audio framework.

Bug: 336658618
Bug: 347781402
Test: m com.android.btservices
Test: Manual streaming test on pixel 6a
Flag: bluetooth.a2dp_aidl_encoding_interval
Change-Id: Ib80558184e094b801066bd1a4d7477dd9315382c