bluetooth: Add support for linux bluetooth raw hci sockets

The implementation is imported from
packages/modules/Bluetooth/system/vendor_libs/linux/interface
with modifications to modernize the code.

The default bluetooth HAL implementation now jointly uses
the serial implementation and the bluetooth socket
implementation.

Bug: 205758693
Test: VtsHalBluetoothTargetTest
Change-Id: I791fd406e56a0144e1117cb6f8e27ec71b48a192