WebGPURenderer: update Line2NodeMaterial and InstancedPointsNodeMaterial

[aardgoose]

Update TSL to remove hacks using property() to force variable assignments into the correct locations.
Use lengthSq() in InstancedPointsNodeMaterial.
trimSegment() is now a real function, not inlined.
.

@sunag dashed mode for Line2 was broken since #28585

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	685.1 kB 169.6 kB	685.1 kB 169.6 kB	+0 B +0 B
WebGPU	823 kB 220.9 kB	822.9 kB 220.8 kB	-162 B -59 B
WebGPU Nodes	822.6 kB 220.8 kB	822.5 kB 220.7 kB	+257 B +35 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	461.9 kB 111.4 kB	461.9 kB 111.4 kB	+0 B +0 B
WebGPU	522.1 kB 140.8 kB	522.1 kB 140.8 kB	+0 B +0 B
WebGPU Nodes	478.8 kB 130.6 kB	478.8 kB 130.6 kB	-43.34 kB +0 B

[Mugen87]

So this PR fixes #28884?

[aardgoose]

No, just a tidy up. just raising the profile of the problem

[mrdoob]

@sunag

What's going on with these WebGPU Nodes results?

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	461.9 kB 111.4 kB	461.9 kB 111.4 kB	+0 B +0 B
WebGPU	522.1 kB 140.8 kB	522.1 kB 140.8 kB	+0 B +0 B
WebGPU Nodes	478.8 kB 130.6 kB	478.8 kB 130.6 kB	-43.34 kB +0 B