Feature/Fix greedy drains

[kklingenberg]

This PR fixes an issue with the pattern:

await new Promise((resolve) => writable.once("drain", resolve));

which fails if writable is closed, because the "drain" event won't be emitted. The previous PR #18 attempted to solve this by adding a race: Promise.race(drain, close), but that's problematic as well because it schedules the same "close" event listener multiple times. Also, the use of Promise.race with long-lasting promises can cause memory problems.

This PR fixes this following the pointers laid out in the above issue, given by user brainkim.