MeshDepthMaterial: Support Reversed Depth

[WestLangley]

The higher precision equivalent of gl_FragCoord.z assumes that the depth range is [ - 1, 1 ].

In the case of reversed depth, the depth range is [ 0, 1 ].

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	338.22 78.88	338.31 78.9	+88 B +15 B
WebGPU	560.72 155.17	560.72 155.17	+0 B +0 B
WebGPU Nodes	559.64 154.96	559.64 154.96	+0 B +0 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	469.49 113.56	469.58 113.57	+88 B +15 B
WebGPU	635.72 172.04	635.72 172.04	+0 B +0 B
WebGPU Nodes	590.37 161.29	590.37 161.29	+0 B +0 B