TSL: Ensure 4 byte alignment for instancedArray() and attributeArray()

[sunag]

Fixes #30983

Description

Ensure 4 byte alignment for instancedArray() and attributeArray().

Example:

const testStruct = struct( {
	a: 'vec3',
	b: 'vec3'
} );

const outputBuffer = instancedArray( 2, testStruct ); // return 8 lengths instead of 6

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	337.26 78.64	337.26 78.64	+0 B +0 B
WebGPU	550.56 152.65	550.64 152.68	+76 B +30 B
WebGPU Nodes	549.91 152.5	549.99 152.53	+76 B +31 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	468.12 113.14	468.12 113.14	+0 B +0 B
WebGPU	625.81 169.41	625.95 169.45	+136 B +41 B
WebGPU Nodes	580.66 158.73	580.8 158.77	+136 B +44 B