avrcp: Connect AV when peer connected only AVRCP

This CL implements an old fix that handles the case where peer device
connects only AVRCP and doesn't connect AV.
First service discovery is done for audio src or sink, to assure peer
device's role. Based on that information a2dp connect is being
triggered after 3s delay.

Bug: 296962438
Bug: 328406945
Flag: com.android.bluetooth.flags.avrcp_connect_a2dp_delayed
Test: avatar run --mobly-std-log --include-filter "A2dpTest#test_ad2p_autoconnect_when_only_avrcp_connected" --mobly-options "--verbose" in follow-up CL: aosp/2773107

Change-Id: I143e1ee618605795b1217154200a9fa7d6891fe4