Drawing using Debug2D overlays the editor when using tool script

[Xrayez]

Goost and Godot version:
ca9d585, Godot 3.4

OS/platform/device including version:
Windows 10

Issue description:
Drawing using Debug2D via tool script results in this:

Steps to reproduce:

tool
extends Node2D

func _process(delta):
    Debug2D.clear()
    Debug2D.draw_circle(64)

Not sure if possible to resolve for now, but I think it should be possible to instantiate Debug2D in the canvas item 2D viewport rather than editor (or rather, point Debug2D.canvas_item property to root node in the scene or so), otherwise this should be documented, and behavior prevented by not instantiating Debug2D singleton in the editor itself.

[Xrayez]

I made it work to draw stuff in the editor

This has a little quirk though: the drawing will persist across scenes if not cleared via script prior to that. Which is kind of expected since Debug2D operates globally. This might be a usability issue for some. In this case, perhaps adding some buttons to manually clear the debug draw canvas might be sufficient (or make an editor plugin to do this automatically). But again, drawing in the editor is not the primary use case for this feature, so I treat this as low priority.