GTAONode: Fix AO with WebGL backend.

[Mugen87]

Related issue: #29587 (comment)

Description

The PR fixes GTAONode for the WebGL backend by creating two helper functions getViewPosition() and getSceneUv() which handle WebGPU/WebGL specific uv convention issues.

This logic is also required for the upcoming SSRNode and potentially third-party and app related code.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	689.82 170.9	689.82 170.9	+0 B +0 B
WebGPU	809.73 218.11	810.12 218.24	+395 B +128 B
WebGPU Nodes	809.24 217.98	809.63 218.1	+395 B +126 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	462.84 111.78	462.84 111.78	+0 B +0 B
WebGPU	535.76 144.59	535.76 144.59	+0 B +0 B
WebGPU Nodes	491.87 134.33	491.87 134.33	+0 B +0 B