ShadowNode: Add support for renderer.highPrecision

[shotamatsuda]

Related issue: #30955

Description

This PR multiplies the light shadow matrix and object world matrix on the CPU when renderer.highPrecision is enabled.

This is the shadow maps equivalent of the issue #30955. Shadow maps become unusable at a large distance from the origin (and relatively at a small scale) in WebGPURenderer, because ShadowNode uses world positions multiplied on the GPU. WebGLRenderer has no such issue.

Alternatives

We could use a custom shadow node on the user side, but this is not very feasible because ShadowNode is not a leaf class here.

Doing world origin rebasing would surely solve this precision issue, but the purpose of renderer.highPrecision is to handle such use cases where world origin rebasing is difficult to implement for various reasons, with some performance trade off.

--

Results with a torus knot with a diameter of 1 at 6e6 away from the origin, with renderer.highPrecision enabled for all cases.

	r183	PR
Directional Light
Spot Light

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	360.01 85.46	360.01 85.46	+0 B +0 B
WebGPU	633.56 175.64	633.79 175.73	+236 B +89 B
WebGPU Nodes	631.68 175.35	631.91 175.44	+236 B +89 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	492.21 120.03	492.21 120.03	+0 B +0 B
WebGPU	705.59 190.53	705.82 190.61	+236 B +83 B
WebGPU Nodes	654.8 177.78	655.04 177.86	+236 B +85 B

[shotamatsuda]

Just skipping the high precision path when receivedShadowPositionNode or a context value overrides shadowPositionWorld, though it's not ideal.