BaseMaterial3D Alpha Hash has visible artifacts when distance between material and camera changes

[Calinou]

Related to #64501, #61882 and godotengine/godot-proposals#4651.

Godot version

4.0.alpha14 (could be reproduced as early as e5d7c7d)

System information

Fedora 36, GeForce GTX 1080 (NVIDIA 515.57)

Issue description

BaseMaterial3D Alpha Hash has visible artifacts when distance between material and camera changes
This has been confirmed to happen on AMD GPUs, so it's not NVIDIA-specific.

alpha_hash.mp4

Enabling TAA does not make this issue go away. Adjusting Alpha Hash Scale doesn't fix the problem either (if anything, it can make the pattern even more noticeable).

cc @marstaik

Steps to reproduce

• Create a MeshInstance with a BoxMesh.
• Set the material's albedo color to a transparent color (e.g. alpha set to 0.5, or 128 on the color picker).
• Create a new StandardMaterial3D for the mesh, and set its transparency mode to Alpha Hash.
• Move the camera slowly in the 3D editor, specifically towards the object. Notice how it flickers as the camera moves.

Minimal reproduction project

test_alpha_hash.zip