Add "fish bones" visualization to the Path2D in the Editor

[xiongyaohua]

Describe the project you are working on

City traffic game

Describe the problem or limitation you are having in your project

The direction of Path2D is not clear

Describe the feature / enhancement and how it helps to overcome the problem or limitation

Related with #5716, add fish bones also to Path2D

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

Change the drawing method of Path2D. Something like this

If this enhancement will not be used often, can it be worked around with a few lines of script?

No

Is there a reason why this should be core and not an add-on in the asset library?

Path2D is core

[akien-mga]

Implemented by godotengine/godot#68860.