GD-Integration: Enable HCI layer only for GD

* Use HCI and HAL layer only with legacy stack
* To enable:
     adb shell device_config put bluetooth INIT_gd_hci true

Bug: 162623932
Tag: #gd-refactor
Test: turn BT on and off, pair BT headset, play music
Change-Id: I0addcee5f4f7630a68e76f42d3fa9c207b8f1c67
Merged-In: I0addcee5f4f7630a68e76f42d3fa9c207b8f1c67