WebGLRenderer: Fix setReversed() so reverseDepthBuffer: true works.

[haxiomic]

Fixes #30808

See #29579 (comment)

reverseDepthBuffer: true has been broken since r170

The problem is in WebGLState.setReversed(), code within the function assumes the value of the variable reversed is set, but it is not set until the end of the function

Also adds the example that @CodyJasonBennett wrote originally, closing #29765 and acting as a regression test

[haxiomic]

CC @CodyJasonBennett

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	336.08 78.29	336.08 78.29	+1 B +1 B
WebGPU	532.63 148	532.63 148	+0 B +0 B
WebGPU Nodes	532.1 147.9	532.1 147.9	+0 B +0 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	465.15 112.18	465.16 112.18	+1 B +2 B
WebGPU	604.33 164.01	604.33 164.01	+0 B +0 B
WebGPU Nodes	559.37 153.45	559.37 153.45	+0 B +0 B

[haxiomic]

Added warning