Bluetooth: Enable Multi-A2DP/HFP support for up to 5 devices

* Set config_bluetooth_max_connected_audio_devices to 5

Bug: 64767509
Test: runtest -j32 bluetooth
      connect and disconnect to multiple headsets and car kits
      TestTracker/146725

Change-Id: I211c5683490fd4be00d3379e11e843081c6fb3a6