tests: bsim: Bluetooth: BAP Broadcast update to 2 bis

Update the bsim test for the BAP broadcast to use 2 bis.
This tests a larger part of the code, and also verifies
that we can send and receive on 2 BIS without any ISO errors.

This requires the ADV interval to be a multiple of ISO interval
- 10ms, so the advertising interval has been set to 80ms.

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