vc: Implement Volume Control Profile

 This implements basic version of VCP which allows to control Volume
 Control Service on ther remote side.

 This profile for expose only connect/disconnect/set volume

 Bug: 150670922
 Tag: #feature
 Test: atest --host bluetooth_test_vc
 Sponsor: jpawlowski@

Change-Id: Ie68c333ffece3958d68580fbfd3a86aec1186711