Renderers: Support EXT_texture_norm16 formats.

[pohlt]

Fixed #33193

Description

I added eight (WebGL) / six (WebGPU) new texture formats (specs) for normalized (u)int16.

I successfully tested all six formats with WebGL2, but cannot easily test it with WebGPU (under Linux).

This contribution is funded by Imricor

The original PR #33250 was accidentially closed.

[pohlt]

@Mugen87, sorry, I screwed up with the rebase and removed the branch to replace it with this new branch, which closed the original PR.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	360.06 85.47	360.57 85.58	+514 B +107 B
WebGPU	633.13 175.68	634.03 175.93	+900 B +249 B
WebGPU Nodes	631.25 175.39	632.15 175.63	+900 B +244 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	492.3 120.06	492.88 120.18	+590 B +118 B
WebGPU	705.19 190.56	706.17 190.86	+977 B +296 B
WebGPU Nodes	654.41 177.83	655.39 178.14	+977 B +317 B

[pohlt]

Hey @Mugen87! Thanks a lot for your support to get this PR in so quickly! Very much appreciated. Greetings from Erlangen