Tests: Bluetooth: Add BSIM test of ISO BIS

Adds 2 tests for ISO broadcast.

First test is just a minimal test that sets up a BIG,
transmits data and verifies that it is being received
on the ISO sync receiver.

The second test creates a BIG, disables BT, enables BT,
and the verifies the above.

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