WebGPURenderer: Render bundle work with multiple render targets

[Berthur]

Currently, Three.js supports the WebGPU Render Bundle API through its BundleGroup class. It also supports rendering to multiple render targets on WebGPU.

However, there seems to be no way to use both at the same time. We get a WebGPU error like Attachment state of [RenderPipeline "renderPipeline_NodeMaterial_17"] is not compatible with [RenderBundleEncoder "renderBundleEncoder"]., because the render bundle encoder only contains a single target.

In this pull request, I attempt to add support to multiple render targets when using render bundle, by including all targets in the render bundle encoder.

With this fix, it indeed becomes possible to use these features together. Still, I don't know if this is the best way to do it. I welcome feedback/discussion from someone more familiar with this part of the code.

This contribution is funded by Trimble

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	338.24 79.14	338.24 79.14	+0 B +0 B
WebGPU	584.32 161.46	584.45 161.48	+131 B +21 B
WebGPU Nodes	582.93 161.22	583.06 161.24	+131 B +21 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	469.7 113.74	469.7 113.74	+0 B +0 B
WebGPU	653.67 176.96	653.8 176.98	+131 B +24 B
WebGPU Nodes	607.78 166.14	607.91 166.16	+131 B +24 B