perf: remove extra Promise wrapper for value in fromPromise and toPromise

[negezor]

Summary

Removes unnecessary Promise wrappers. Since Promise can unroll itself, these operations only create overhead

For example:

Promise.resolve()
  .then(() => Promise.resolve(Promise.resolve(Promise.resolve(Promise.resolve(1)))))
  .then((value) => {
    console.log('val', value)
  });

// val 1

And

new Promise(resolve => resolve(Promise.resolve(Promise.resolve(Promise.resolve(Promise.resolve(1))))))
  .then((value) => console.log('val', value));

// val 1

Set of changes

Removing unnecessary Promise wrappers in sources.ts and sinks.ts.

[JoviDeCroock]

These changes are not functionally equivalent, the prior code intends to delay the resolution by a micro tick

[negezor]

But why? This is not used in other parts of the code 🤔 And only non-equivalent one is toPromise.

[kitten]

This is because promise timing doesn't actually mix very well with Wonka.
This can cause subtle race conditions and bugs. In React Native it even used to cause complete stalls.

The cost here is minimal, in fact, the optimal solution with Wonka is to always avoid converting to or from promises, unless it's absolutely necessary or part of a surfaced API.

The problem with immediately resolving promises is that it becomes very easy to chain logic accidentally into a "single tick" when this isn't desired though. Delaying all promise conversions by a micro tick hence gets rid of a whole class of bugs without causing much of a problem