Spwaner: Load controller with remote only .yaml

[mamueluth]

Replaces: #2349
There are cases in which you want to spawn controllers running on a remote machine (robot) without the controllers.yaml beeing available on the local machine. This PR extends the spawner with the option to activate a controller on the remote machine without the need of having controllers.yaml on your local machine.

Example:

ros2 run controller_manager spawner fts_broadcaster:force_torque_sensor_broadcaster/ForceTorqueSensorBroadcaster --param-file /path/to/controllers.yaml --param-file-remote-only

Open questions

1. How to pass controller type? In the spawner we need to know at least the controller name and the controller type. Usually we would parse the type from the controller.yaml but since the file is not present on the local machine we need to pass the type. I choose to do: controller:type as can be seen in the example. Is this good?

2. How should we go about testing? In tests the file will always be present. I would just define the .yaml in code, don't have the file present and test like this or are there any other suggestions?

[saikishor]

If i understood correctly it expects that the file exist on the same PC as the controller manager. I thought this PR is for cases when you want to load files of PC launching the command, but not on the PC the controller_manager is running

[mamueluth]

If i understood correctly it expects that the file exist on the same PC as the controller manager. I thought this PR is for cases when you want to load files of PC launching the command, but not on the PC the controller_manager is running

No its inverted its for cases where you don't have the .yaml file local but it exists on the remote machine (robot).

I wanted to add the inverse as well if we want this.