WebGPURenderer: Restore isSampledTexture3D binding check

[sunag]

Related issue: #31175

Description

Restore isSampledTexture3D binding check and fix webgpu_postprocessing_3dlut example and Data3DTexture.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	337.71 78.77	337.71 78.77	+0 B +0 B
WebGPU	557.9 154.38	557.91 154.39	+5 B +8 B
WebGPU Nodes	556.83 154.17	556.83 154.18	+5 B +9 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	468.94 113.46	468.94 113.46	+0 B +0 B
WebGPU	633.27 171.37	633.27 171.38	+5 B +7 B
WebGPU Nodes	588.32 160.71	588.33 160.72	+5 B +8 B