Unify and simplify source code generation

[adam-enko]

Source code generation is very similar for Native, JS, and Wasm platforms.

This and GenerateWasmSourceWorker are almost identical. The only exceptions are useBenchmarkJs param and a platform supplied to SuiteSourceGenerator.

Perhaps, we can use a single set of classes (worker and parameters) instead?

Originally posted by @fzhinkin in #235 (comment)

This could most likely be simplified.

If the workers were merged, then it would make sense merge all of the Native/JS/Wasm generation into a single worker and task. They don't differ significantly: Native uses KlibResolver.Native and JS/Wasm uses KlibResolver.JS, and this can be controlled with a Platform input property.

It's a bit delicate to do such refactoring at the moment because the Native worker is in the public API, but will be easier once the visibility of workers is limited #211.