Add A2DP src and sink co-exist feature init::flag (5/5)

[Description]
Add A2DP src and sink co-exist feature, that we can connect
both sink and src remote device at the same time while only
keep 1 streaming.
Add property “bluetooth.a2dp.src_sink_coexist.enabled” to control this feature

Bug: 256938279
Test: A2DP src/sink connect, streaming successully,
net_test_btif_rc unit test pass

Change-Id: I89ee8391f73daffaa992a5e7fafba36635a19641