samples: sensor: sensor_shell: Added channels count for sensor_shell tests

Use of the `sensor get` help. No channel provided allows the sensor_shell
to iterate through every channels. Getting the last channel gives the last
channel index and therefor the channel count. Provide futur proofing for
new channels.

Signed-off-by: Logan Saint-Germain <l.saintgermain@catie.fr>

Author: Sokario

samples/sensor/sensor_shell/pytest/test_sensor_shell.py

@@ -20,11 +20,14 @@ def test_sensor_shell_info(shell: Shell):
 
 
 def test_sensor_shell_get(shell: Shell):
-    logger.info('send "sensor get" command')
+    logger.info('get "sensor get" command count')
+
+    lines = shell.exec_command('sensor get sensor@0')
+    channel_count = int(lines[-2].split("=")[1].split("(")[0]) + 1
+    logger.info(f'channel count: [{channel_count}]')
 
-    # Channel should be the last one before 'all' (because 'all' doesn't print anything) so that the
-    # for-loop in `parse_named_int()` will go through everything
-    for channel in range(65):
+    logger.info('send "sensor get" command')
+    for channel in range(channel_count):
         logger.info(f'channel {channel}')
         shell.wait_for_prompt()
         lines = shell.exec_command(f'sensor get sensor@0 {channel}')