Bluetooth: controller: Implement LE Create BIG Test command

Implement test version of the LE Create BIG command ll_big_test_create
(BT_HCI_OP_LE_CREATE_BIG_TEST) in the controller.

This enables use of CONFIG_BT_ISO_ADVANCED, which supports use of
the following BIG/QoS configuration parameters (otherwise derived):

- ISO_Interval
- NSE
- Max_PDU
- BN
- IRC
- PTO

Signed-off-by: Morten Priess <mtpr@oticon.com>