Rewrite the scan topic costmap plugins for multi-robot(namespace)

before launch navigation.

Author: hyunseok-yang

nav2_bringup/launch/navigation_launch.py

@@ -59,7 +59,8 @@ def generate_launch_description():
 
     # Create our own temporary YAML files that include substitutions
     param_substitutions = {
-        'autostart': autostart}
+        'autostart': autostart,
+        'topic': (namespace, '/scan')}
 
     configured_params = RewrittenYaml(
         source_file=params_file,