Draw fewer fishbones to improve Path gizmo readability and performance

[Calinou]

This affects both Path2D and Path3D.

• This partially addresses Add option to disable Path2D/3D fish bone debug visuals godot-proposals#9459.

Testing project: test_fish_bones.zip

Preview

Top-left corner: Path2D
Bottom-right corner: Path3D

Before	After

[fire]

Did not review the code, but the screenshots do seem to help usability

[akien-mga]

Looks fine overall.

Both before and after though, I wonder why those look like this in the bottom right part of the curve:

There seems to be room for improvement of how they're calculated to be a bit more tangential to the curve and more visible. But that's out of scope of this PR.

[akien-mga]

Thanks!

[Calinou]

Both before and after though, I wonder why those look like this in the bottom right part of the curve:

There are only 3 vertices for each fishbone even in 3D space, so depending on the angle relative to the camera, these can appear to be almost flat. If we added 3 more vertices on top of it to draw the arrow in a "cross" shape, it would be more visible, but you would lose the information on the path's tilt angle (which matters for some scenarios).

I wonder what other engines do here.