WebGPU: Fix FrontFace

[sunag]

Description

In some comparative tests, I notice that built-in front_facing, it is NormalMap was inverted because of the direction of frontFace.

This contribution is funded by Google via Igalia

[WestLangley]

Oh, no.

Front faces have counter-clockwise winding order in three.js. With this PR, when material.side is front-sided, then so-called "front faces" are culled.

We can't do this. This is going to cause incredible confusion as we try to get normal mapping correct inside the shader.

Furthermore, back-faces with normal maps are still not correct.

Normal mapping has to be corrected by other methods -- via normalScale, and WebGPU-specific shader mods.

[sunag]

I can't see any visual difference after this PR between WebGL and WebGPU referring to normal direction.

This is the test of AB:

WebGPU	WebGL	Side
		Front
		Back

WebGPU - A
WebGL - B

The idea is not to use hacks or shaders mods, I think this should be an approach to be abolished if possible.
NodeMaterial should work on any backend using the same shader graph.

About the PR, do you think this might be related to the NDC?

[WestLangley]

I think there will be issues related to the different viewport transform in WebGPU.

WebGPU has different pipeline conventions than WebGL, so I expect the normal/bumpmap shader code may have to be modified.

Can you test viewing a back face in WebGPU when material.side = THREE.BackSide and when material.side = THREE.DoubleSide. The back faces should appear the same in those two test cases.

Also, AFAIK, it has not been specified whether WebGPU will support the DirectX normal map convention. I assume that will be the case. three.js uses the OpenGL convention.