TSL: use vec3 for DataArrayTexture UV coordinates

[zonkypop]

Description

When using DataArrayTexture with the WebGLBackend, TSL's generateUV by default uses only the .xy for sampling textures, this causes shader compile errors when using a texture node with an DataArrayTexture. This is a simple fix which makes the uvSnippet use a vec3 instead when we have a DataArrayTexture.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	336.65 78.39	336.65 78.39	+0 B +0 B
WebGPU	522.23 144.94	522.28 144.96	+50 B +20 B
WebGPU Nodes	521.7 144.84	521.75 144.85	+50 B +20 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	465.64 112.24	465.64 112.24	+0 B +0 B
WebGPU	592.61 160.56	592.66 160.58	+50 B +22 B
WebGPU Nodes	547.74 150	547.79 150.02	+50 B +20 B

[zonkypop]

Looks like this breaks a lot 😱

A reproducible example is running: https://threejs.org/examples/?q=webgpu#webgpu_textures_2d-array

In fallback/GL mode with:

material.colorNode = texture( map, coord )

instead of:

material.colorNode = texture( map, coord ).depth( oscLayers ).r.remap( 0, 1, - .1, 1.8 );

adding: .depth( oscLayers ) will fix any compile errors.

I'm not sure if adding the depth there is expected / intentional, or if it is supposed to work with a vec3?