WebGPURenderer: Fix texture compare fallback for shadows.

[Mugen87]

Fixed #33048.

Description

#33048 showed that a few bits for Android are missing to make PCF shadows work correctly.

• In TextureNode, all less and greater compare functions must be handled and mapped to the correct step() fallback (that's also important for reversed depth buffer).
• Deactivate linear filtering when texture comparison isn't supported (use the default nearest filtering of depth textures).

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	359.17 85.24	359.17 85.24	+0 B +0 B
WebGPU	626.25 174.04	626.44 174.13	+186 B +80 B
WebGPU Nodes	624.83 173.8	625.02 173.88	+186 B +79 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	490.91 119.65	490.91 119.65	+0 B +0 B
WebGPU	699.88 189.07	700.06 189.13	+181 B +60 B
WebGPU Nodes	649.09 176.43	649.27 176.49	+181 B +61 B