Create command "Regenerate GTraits Script"

[jpaugh]

This exposes the regenerate functionality to the user through the Editor > Command Palette menu in addition to the keyboard shortcut.

• Refactor Ctrl+Alt+U shortcut action to a separate function
• Register that function as a command when we _enter_tree
• De-register the function when we _exit_tree

[jpaugh]

Here's what it looks like in the editor:

[Earewien]

Hey !

This is a nice addition to this addon, again thank you for your participation.

Is it possible for me to request some (minor) changes to maintain code consistency ? If so, I will make a quick review of your PR.

Again, thank you !

[jpaugh]

You're the boss! I'm unfamiliar with your coding style, and I know how important consistency is for sanity.

[jpaugh]

I got those style changes done. Sorry it took me so long! I went off the deep end trying out Rust game engines, and then settled on Godot again. ;-)