Core: Std_ToggleTransparency: Fixes #11353

[PaddleStroke]

Fixes #11353 :

• Groups now toggling their content correctly.
• The command toggle the PD body instead of the tip
• The command placement in the View menu is fixed.

[maxwxyz]

@PaddleStroke nice! could the check tip (toggle body) be also implemented in the spacebar / toggle visibility command, only for selection in the viewport?

[PaddleStroke]

I guess it's possible to implement that for visibility as well. But if you want to hide the tip and show another feature. As you say it could be only if selected in the viewport. I think this needs discussion.