TSL: Align API of blur filters and deprecated premultipliedGaussianBlur()

[sunag]

Related issue: #31557 (comment)

Description

• Remove option.mask parameter, use .sample() instead.
• Align API of blur filters and deprecated premultipliedGaussianBlur().

const maskReflection = sample( ( uv ) => {

	const sample = reflection.sample( uv );
	const mask = reflectionDepth.sample( uv );

	return vec4( sample.rgb, sample.a.mul( mask.r ) );

}, reflection.uvNode );

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	338.62 79.03	338.62 79.03	+0 B +0 B
WebGPU	566.43 156.57	566.48 156.58	+52 B +14 B
WebGPU Nodes	565.03 156.32	565.09 156.34	+52 B +14 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	470.05 113.73	470.05 113.73	+0 B +0 B
WebGPU	637.91 172.58	637.91 172.58	+0 B +0 B
WebGPU Nodes	592.56 161.85	592.56 161.85	+0 B +0 B

[sunag]

@Mugen87 I'm doing something a bit different — instead of aligning all the different blur options, we can use the new .sample() interface. This way, we won’t have to worry as much if developers need more customized features in the future. We can do the same with premultiplyAlpha too.