Adding scratch/snap-like visual scripting

[akasob]

As you know, the visual script will be removed in version 4.
In this regard, I propose to consider the possibility of creating a Scratch-style visual scripting system for Godot.
Here are examples of how it might look in comparison with the old scripting.
Compare how much more concise a block script is than a node script.

[Calinou]

This is already being tracked in godotengine/godot-visual-script#27 and godotengine/godot-visual-script#29.