tests: Bluetooth: BAP: Add broadcast tests with multiple subgroups

Add 4 new tests for BAP broadcast:
1) One subgroup with one stream per subgroup
2) One subgroup with two streams per subgroup
3) Two subgroups with one stream per subgroup
4) Two subgroup with two streams per subgroup

To support these, the number of broadcast streams and data paths
was updated to be up to 4.

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