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.