Variables: Allow deletion

[manuq]

What Happened

Variables can be created from the Variables section using the "+ Create New Variable" button. But they can't be removed. Add UI below the "+ Create New Variable" button to remove existing variables. This could be a "🗑 Remove Variable" dropdown, with a confirmation dialogue.

How to Reproduce

N/A

Block Coding Plugin Version

main

Godot Engine Version

4.3

Operating System

Endless OS

Logs or command-line output

Anything else?

No response