Add possibility to set use_sim_time as launch argument.

[larshg]

Use LaunchArg for monitor_dynamics as well.

For reference: #1810 #1811

https://robotics.stackexchange.com/questions/104444/use-sim-time-with-moveit

Allows you to call it like:

ros2 launch panda_moveit_config move_group.launch.py use_sim_time:=True

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