WebGPURenderer: Fix texture issues.

[Mugen87]

Related issue: #33250

Description

#33250 encountered a few minor issues in the WebGL 2 backend of WebGPURenderer that should be fixed separately.

• In Info, the texture memory size for various formats was not computed correctly.
• The WebGL 2 backend used invalid texture formats gl.R16, gl.RG16, gl.RGB16, gl.RGBA16
• When a non-integer format (e.g. gl.RED) is used with gl.BYTE, a SNORM internal format should be selected and not an integer one (e.g. R8_SNORM instead of R8I).
• Integer internal formats like R32I are only used with integer formats now.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	360.06 85.47	360.06 85.47	+0 B +0 B
WebGPU	633.59 175.7	633.13 175.68	-462 B -22 B
WebGPU Nodes	631.71 175.41	631.25 175.39	-462 B -22 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	492.3 120.06	492.3 120.06	+0 B +0 B
WebGPU	705.65 190.59	705.19 190.56	-459 B -24 B
WebGPU Nodes	654.87 177.85	654.41 177.83	-459 B -23 B