tests: Bluetooth: Tester: Add new BT controller config

Adds a new BT controller configuration that can be applied
to multiple boards and not specific to the nRF5340 cpunet
as the existing setup uses from hci_ipc.

The config is based on nrf5340_cpunet_iso-bt_ll_sw_split.conf
from hci_ipc sample.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>