Allow for the Collision Object to get shapes from nested children

[Wokarol]

Describe the project you are working on

This issue is not part of a project but rather "is that engine good for my games" research.
But to present the problem in more realistic scenario, let's assume a 2D Robot arm that can hit the player.

Describe the problem or limitation you are having in your project

It would be natural and convenient to be able to parent the shapes to the given segments of the robot, like shown here:

It's not possible as the shape has to be a direct child of the collision object

Describe the feature / enhancement and how it helps to overcome the problem or limitation

The fix for that would be to allow for gathering the shapes from nested children too.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

It would be a flag on a collision object

If this enhancement will not be used often, can it be worked around with a few lines of script?

It can be worked around using Remote Transforms, but that solution is not modular nor scalable. You can see how that would get ugly and very messy fast

Is there a reason why this should be core and not an add-on in the asset library?

It's a modification to a built-in node and a common game feature

[Calinou]

Duplicate of #535.