WebGPURenderer: Improve shader validation

[sunag]

Description

Improves shader validation and prevents WebGPUBackend from completely crashing if one of the shaders fails to compile.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	350.11 84.81	350.11 84.81	+0 B +0 B
WebGPU	604.78 169.56	605.06 169.68	+282 B +119 B
WebGPU Nodes	603.39 169.32	603.67 169.44	+282 B +115 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	481.77 119.56	481.77 119.56	+0 B +0 B
WebGPU	674.15 185.03	674.44 185.15	+285 B +117 B
WebGPU Nodes	616.15 168.26	616.43 168.38	+285 B +121 B