[Little UI improvement] Clone all main UI available A3 commands into the top Assembly3 drop-down menu

[YosypC]

It's no mystery that the FreeCAD UI hasn't been designed by a PhD UX designer, hence it brings some usability issues that can be optimized. A good workflow of mine for when I encounter a new workbench or software in general, is first browsing what they generally offer in the most schematic way possible to tidy my mind up.

It seems that only the basics A3 commands are available under the drop-down menu, and it makes harder for me to study the workbench.
The " | " separated UI commands are enough but I find them confusing in the default order, and a bit hard to customize.