Bluetooth: Implement support for Mesh

The patch adds state bits, storage and HCI command chains for sending
and receiving Bluetooth Mesh advertising packets, and delivery to
requesting user space processes. It specifically creates 4 new MGMT
commands and 2 new MGMT events:

MGMT_OP_SET_MESH_RECEIVER - Sets passive scan parameters and a list of
AD Types which will trigger Mesh Packet Received events

MGMT_OP_MESH_READ_FEATURES - Returns information on how many outbound
Mesh packets can be simultaneously queued, and what the currently queued
handles are.

MGMT_OP_MESH_SEND - Command to queue a specific outbound Mesh packet,
with the number of times it should be sent, and the BD Addr to use.
Discrete advertisments are added to the ADV Instance list.

MGMT_OP_MESH_SEND_CANCEL - Command to cancel a prior outbound message
request.

MGMT_EV_MESH_DEVICE_FOUND - Event to deliver entire received Mesh
Advertisement packet, along with timing information.

MGMT_EV_MESH_PACKET_CMPLT - Event to indicate that an outbound packet is
no longer queued for delivery.

Signed-off-by: Brian Gix <brian.gix@intel.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>