WebGPURenderer: Improve cache bindings from node uniforms

[sunag]

Related issue: #32243

Description

It reuses the binding classes generated by nodes, avoiding some unnecessary updates and saving memory.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	356.24 86.48	356.24 86.48	+0 B +0 B
WebGPU	613.34 172.13	613.68 172.23	+337 B +92 B
WebGPU Nodes	611.95 171.88	612.28 171.97	+337 B +92 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	488.02 121.25	488.02 121.25	+0 B +0 B
WebGPU	682.75 187.41	683.09 187.49	+337 B +77 B
WebGPU Nodes	624.47 170.62	624.81 170.73	+337 B +103 B

[sunag]

To reproduce o problem.

1. Create a buffer and share it in two Material.
2. Previously it would update the buffer twice in Backend.updateBinding() in the same render call, now only once.

const array = new Float32Array( 8 * 4 );
array.set( [ 1, 0, 0, 1 ] ); // red

const bufferArray = buffer( array, 'vec4', 3 ).setGroup( renderGroup );

// share it

materialA.colorNode = bufferArray.element( 0 );
materialB.colorNode = bufferArray.element( 0 );