Use `choice` XML tag in .launch.xml files

[destogl]

Add this to the example launch files to keep the knowledge about it.

Here the example:

<arg name="log_level_driver" default="info" description="Set the logging level of the loggers of all started nodes.">
      <choice value="debug"/>
      <choice value="DEBUG"/>
      <choice value="info"/>
      <choice value="INFO"/>
      <choice value="warn"/>
      <choice value="WARN"/>
      <choice value="error"/>
      <choice value="ERROR"/>
      <choice value="fatal"/>
      <choice value="FATAL"/>
  </arg>