WebGPURenderer: Add mat2 uniform support

[RenaudRohlinger]

Related: #30364

Description

Following #30364, after adding mat2 support in TSL, this PR adds support for mat2 uniforms in the WebGPURenderer.

This contribution is funded by Utsubo

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	336.25 78.28	336.25 78.28	+0 B +0 B
WebGPU	505.84 140.49	506.14 140.5	+301 B +16 B
WebGPU Nodes	505.31 140.38	505.61 140.4	+301 B +18 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	465.25 112.13	465.25 112.13	+0 B +0 B
WebGPU	579.87 157.17	580.18 157.21	+302 B +45 B
WebGPU Nodes	535.26 146.73	535.56 146.78	+302 B +58 B