[Pandora] - Enable A2DP/SNK/CC Tests

* Allow null proxy to have a2dp sink and source
on the same run.
* Enable the following test:
A2DP/SNK/CC/BV-01-I
A2DP/SNK/CC/BV-02-I
A2DP/SNK/CC/BV-05-I
A2DP/SNK/CC/BV-06-I
A2DP/SNK/CC/BV-07-I
A2DP/SNK/CC/BV-08-I

Bug: 240324621
Test: atest pts-bot:A2DP
Change-Id: Idd2e1e7dab3a78fb6a0a8616b692f41a6468edc3