NodeMaterial: Remove shadowPositionNode fallback to reduce CPU load.

[Mugen87]

Related issue: #32675

Description

When investigating #32675, I have found out the root cause for the performance regression in r176 was #30962. I couldn't explain why #30962 increases the CPU load until I remember there were issues with Object.defineProperty(). I've simply removed the call from NodeMaterial and the CPU load reduced noticeably (from 46% to 34 % measured with Chrome Task Manager).

The example from #32675 (comment) is a bit of a edge case because it creates many individual materials (10000) but something similar can also happen in real-world scenarios with many individual render items.

I did not add real getter/setter as a replacement since that would include shadowPositionNode into getMaterialCacheKey(). Given the deprecated status, I think it's okay to bump the property now and get less CPU load in exchange.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	355.36 84.47	355.36 84.47	+0 B +0 B
WebGPU	621.33 172.53	621.11 172.47	-221 B -61 B
WebGPU Nodes	619.93 172.29	619.71 172.23	-221 B -58 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	487.31 119.25	487.31 119.25	+0 B +0 B
WebGPU	692.57 187.86	692.34 187.8	-222 B -56 B
WebGPU Nodes	642.37 175.08	642.14 175.03	-222 B -54 B

[sunag]

I think this will need refactoring as well?

[Mugen87]

I'm not sure. I did not see a CPU lload reduction when removing the Object.defineProperty() usage in other classes e.g. Node. Maybe it's because shadowPositionNode had a setter?