TSL: Improve fog approach.

[sunag]

Related issue: Fixes #30077

Description

Improve TSL fog apporach.
This allows you to manipulate the fog more easily, where the factor and colors are separated.

• Added rangeFogFactor, densityFogFactor
• fog() -> vec4( color, factor )

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	339.21 79.01	339.21 79.01	+0 B +0 B
WebGPU	485.99 134.91	485.82 134.88	-168 B -31 B
WebGPU Nodes	485.45 134.81	485.29 134.78	-168 B -31 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	465.1 112.06	465.1 112.06	+0 B +0 B
WebGPU	555.39 150.39	554.93 150.31	-459 B -86 B
WebGPU Nodes	511.24 140.09	510.78 140.01	-459 B -76 B