NodeMaterialObserver: Avoid usage of Object.keys().

[Mugen87]

Fixed #33107.

Description

The PR is an alternative to #33111 with a more simple and less invasive approach. Object.keys() in equals() is replaced with for...in loops which avoids any object allocations during the attribute comparison process.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	359.27 85.31	359.27 85.31	+0 B +0 B
WebGPU	629.94 174.99	629.93 174.99	-11 B +0 B
WebGPU Nodes	628.52 174.74	628.51 174.74	-11 B +1 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	491.03 119.72	491.03 119.72	+0 B +0 B
WebGPU	703.56 189.99	703.55 189.99	-11 B +1 B
WebGPU Nodes	652.77 177.37	652.76 177.37	-11 B +2 B