LeAudioTestApp/Bass: Allow channel selection

Numerical imput allows to set channel preference map.

For example value of 3 (0b11) selects channel #1 and #2,
4 (0b100) selects channel #3 and so on.

Tag: #feature
Bug: 240885642
Test: manual - logs verification
Change-Id: I0a5ed3c2b8b9b12a7df9848fc947cb3aecfdcdf4
Merged-In: I0a5ed3c2b8b9b12a7df9848fc947cb3aecfdcdf4
(cherry picked from commit 84a3384a)