samples: sensor:shell: test all channels

Loop through all of the channels and make sure that each
channel has an output.

Changes in patch originally present in #72972.

Signed-off-by: Yong Cong Sin <ycsin@meta.com>
Signed-off-by: Luis Ubieda <luisf@croxel.com>
(cherry picked from commit 1e64d7be)