Tree-shaking: ShaderLib and UniformsLib

[pschroen]

Related issue: #24199

Troubleshooting the remaining side-effects, converted both ShaderLib and UniformsLib to static class fields for discussion added pure annotations.

[Mugen87]

If it helps improving tree-shaking, I'm fine with this PR.

That said, I'm a bit frustrated with cluttering the code base with annotations and refactoring easy-to-read code to something more incomprehensible 😞 . However, seems like there is no way around it if we want smaller bundles.

[pschroen]

@Mugen87 I agree, I hate adding /*@__PURE__*/ annotations everywhere, it's a hack, and there are ways to write a library that is tree-shakable with no pure annotations.

It would require a pretty major re-write though, and everything would need to be self-contained classes.

I should also point-out there is a way around it, exporting your source files as the library entry point. These are all flat bundle problems. See #24006 (comment) 😜

[mrdoob]

Thanks!