WebGPURenderer: Improve support int/uint textures

[sunag]

Related issue: #27879

Description

Improve support int/uint textures for WGSL.

[Spiri0]

I have now implemented your extensions in r162 and it works fine. I need to take a closer look at all of this to understand it better.
I use this in my virtual texture system

This is an older screenshot from a week ago.
Meanwhile it's even better because I've also included the normal maps and calculated the tbn matrix and light. The model is from the internet. The model uvs are not ideal for virtual texturing and the textures could be much higher resolution but it still works very well.

I didn't expect the extension to be so extensive, but it helps me better understand how three.js works. Those were quite a few changes at the deepest level that you made.