Visualize wrenches applied on links

[chapulina]

When applying lots of different wrenches to a link using Link::AddWorldWrench, it's difficult to debug the simulation and tell what forces are applied where and with what magnitude. It would be simpler to debug simulation if it was possible to visualize these forces in 3D.

Desired behavior

Give users the option of visualizing forces applied to links by various plugins while simulation is running. It's important to be able to tell apart what plugins are applying which forces, and to disable the visualization in case users are not interested in them and they're getting in the way.

Alternatives considered

Debugging forces with 2D plots and print statements is also valuable, but less intuitive.

Implementation suggestion

It makes sense to use markers to manage the visualization. ign-msgs already has an ARROW type, but that's not handled by the MarkerManager yet. We could either add arrow support, or implement this first with lines or cylinders, and come back to arrows later.

Various plugins apply forces, so to avoid duplication, we should add a helper function that can be used by all plugins to visualize their forces. It probably makes sense to pair the functionality with the existing Link::AddWorldWrench function. Each plugin should expose SDF elements to configure their visualizations (i.e. color, scaling...), and we may want to have a helper function to parse this too.

Additional context

This is especially useful for marine applications, where we have multiple plugins applying various forces.