Use of BaseViewer selection mechanism to add live selection feedback in the 3D view

[damienmarchal]

During discussion about the removal of every showXXX in object (as in sofa-framework/sofa#5591) it was pointed that having display component in the scene cover one use case... but not the "scene" debugging one, so as asked by @hugtalbot, here is a draft of live "showXXX" implemented "out of the scene".

For the moment this is just for drafting as there is a lot to do in a different way, especially the rendering of the different type of objects. In the PR, it is based on the data field's name and dynamic_cast... (see drawSelection method). This is clearly a questionable design. Moving all this code in Sofa.Gui.Common is probably to consider because the "selection" rendering code & logic can/may/should be shared by all the GUIs instead of implemented in each of them.

To activate use the -i (interactive) mode is on, so no consequences for default uses.

Possible things to do to move forward:

• decide a software architecture to pick the right rendering code depending on the selected object (keeping or not the data's name & type selection)
• move that in Sofa.GUI.Common (so in Sofa) so it is shared with imGUI
• implement the same in imGUI
• in Sofa.Qt add a panel somewhere to control whether or not we want to rendering bbox, points, frames, their scale, indices ... etc...
• extend the code to handle multiSelection (even if runSofa does not support it)

A Small video:

[damienmarchal]

In commit 5076097 I added setting's to control whether or not we activate the selection rendering.

I also moved the Viewer's shortcuts in a dialog in the Help menu which lead to: