gh-129288: Add optional l2_cid and l2_bdaddr_type in BTPROTO_L2CAP socket address tuple (#129293)

Add two optional, traling elements in the AF_BLUETOOTH socket address tuple:

- l2_cid, to allow e.g raw LE ATT connections
- l2_bdaddr_type. To be able to connect L2CAP sockets to Bluetooth LE devices,
  the l2_bdaddr_type must be set to BDADDR_LE_PUBLIC or BDADDR_LE_RANDOM.