TSL: Introduce clipSpace

[sunag]

Fixes #32583 (comment)

Description

Adds clipSpace and rebuilds positionView from clipSpace if material.vertexNode is used.

This should correct view-z discrepancies in custom shaders at the vertexNode.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	355.34 84.47	355.34 84.47	+0 B +0 B
WebGPU	617.86 171.37	618.29 171.69	+434 B +316 B
WebGPU Nodes	616.46 171.13	616.89 171.44	+434 B +312 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	487.5 119.33	487.5 119.33	+0 B +0 B
WebGPU	689.3 187.14	690.55 187.34	+1.25 kB +198 B
WebGPU Nodes	639.15 174.35	640.39 174.58	+1.25 kB +224 B

[Mugen87]

Tested locally with the repro case from the OP and the issue is indeed fixed! 🎉

[sunag]

I also need to optimize it so that clipSpace is only declared when it is used.

[Mugen87]

While testing the latest shadow map changes, I've realized webgpu_shadowmap_progressive is broken on dev. The light map isn't properly applied to the scene anymore. After some testing it turned out this particular change is the root cause.

I'm not sure how to fix this but ProgressiveLightMap assigns custom code to vertexNode. Is that a help? Unfortunately, #32691 does not fix the example.