Shift the bluetooth packages into variables

Bluetooth packages have been shifter to variables defined in
bluetooth block configuration file. VIRTUAL_RUNTIME_* are used to
specify runtime depencies and bluetooth-stack is used to specify
build time dependcy. Also bluez5 has been set as default in
bluetooth block configuration file (bluetooth.conf).

Signed-off-by: Fahad Arslan <fahad_arslan@mentor.com>