leaudio/testapp: Select Broadcast Audio parameters with context type

This allow the test app to create various BIG configurations needed to
pass qualification tests.

Bug: 230340466
Tag: #feature
Sponsor: jpawlowski@
Test: atest LeAudioBroadcastServiceTest
Change-Id: I23bb0ccf92eed097f3d20065f96e3b68beafc563