This makes a cleaner separation between the: driver, HCI UART and BT stack.
Also updated the naming to be more consistent (mp_bluetooth_hci_*).
Work done in collaboration with Jim Mussared aka @jimmo.
Move extmod/modbluetooth_nimble.* to extmod/nimble. And move common
Makefile lines to extmod/nimble/nimble.mk (which was previously only used
by stm32). This allows (upcoming) btstack to follow a similar structure.
Work done in collaboration with Jim Mussared aka @jimmo.
Damien George