LE Audio: Add ISO part to broadcast audio bsim tests

[Thalley]

Is your enhancement proposal related to a problem? Please describe.
Broadcast ISO should be working in the babblesim now, and as such the broadcast audio bsim tests can be expanded upon to fully utilize the API.

Describe the solution you'd like
The babblesim tests need to fully use the API including creating and syncing to the BIG.

Describe alternatives you've considered
N/A

Additional context
N/A