WebGPURenderer: Add cube face to readRenderTargetPixelsAsync parameters

[aardgoose]

Related issue: comment

Add support reading cube textures to readRenderTargetPixelsAsync().

Not tested with cube textures.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	685.2 kB 169.6 kB	685.2 kB 169.6 kB	+0 B +0 B
WebGPU	823 kB 220.9 kB	823.1 kB 220.9 kB	+80 B +12 B
WebGPU Nodes	822.6 kB 220.8 kB	822.7 kB 220.8 kB	+499 B +106 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	462 kB 111.5 kB	462 kB 111.5 kB	+0 B +0 B
WebGPU	522.1 kB 140.8 kB	522.2 kB 140.8 kB	+80 B +14 B
WebGPU Nodes	478.8 kB 130.6 kB	478.9 kB 130.6 kB	-43.26 kB +13 B

[aardgoose]

This appears to work with a hacked LightProbeGenerator with the WebGL fallback but the differences in texture coordinates and appear to be causing issues for the WebGPU path.

[Mugen87]

But that is a separate issue right? The changes to readRenderTargetPixelsAsync() look correct, imo.

[aardgoose]

Yes, it works, how the data returned is handled just needs addressing.