WebGPURenderer: Rework to use a single renderBundle per Group().static object

[aardgoose]

The existing code uses a renderBundle per object. Create a single renderBundle in preparation for bindGroup sorting and setBindGroup() minimisation,using a renderBundle currentSet{} object.

This combined with PR #27388 (single buffer for uniform buffers), I get a Chrome GPU Process frame time reduced from 10ms to 1.5ms.

[github-actions[bot]]

📦 Bundle size

Full ESM build, minified and gzipped.

Filesize dev	Filesize PR	Diff
685.4 kB (169.7 kB)	685.4 kB (169.7 kB)	+0 B

🌳 Bundle size after tree-shaking

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

Filesize dev	Filesize PR	Diff
462 kB (111.4 kB)	462 kB (111.4 kB)	+0 B