demo: replace individual launch files with common run.launch.py

Launch individual binaries with:
ros2 launch moveit_task_constructor_demo run.launch.py exe:=<binary>

Author: rhaschke

demo/launch/cartesian.launch.py

@@ -1,4 +1,6 @@
 from launch import LaunchDescription
+from launch.actions import DeclareLaunchArgument
+from launch.substitutions import LaunchConfiguration
 from launch_ros.actions import Node
 from moveit_configs_utils import MoveItConfigsBuilder
 
@@ -7,21 +9,21 @@ def generate_launch_description():
     moveit_config = (
         MoveItConfigsBuilder("moveit_resources_panda")
         .robot_description(file_path="config/panda.urdf.xacro")
-        .planning_pipelines(pipelines=["ompl"])
         .to_moveit_configs()
     )
 
-    cartesian_task = Node(
+    node = Node(
         package="moveit_task_constructor_demo",
-        executable="alternative_path_costs",
+        executable=LaunchConfiguration("exe"),
         output="screen",
         parameters=[
-            moveit_config.joint_limits,
             moveit_config.robot_description,
             moveit_config.robot_description_semantic,
             moveit_config.robot_description_kinematics,
+            moveit_config.joint_limits,
             moveit_config.planning_pipelines,
         ],
     )
 
-    return LaunchDescription([cartesian_task])
+    arg = DeclareLaunchArgument(name="exe")
+    return LaunchDescription([arg, node])