AbortSignal support

[BerkliumBirb]

No description provided.

[mdlavin]

@BerkliumBirb thank you for the improvement and especially thank you for the testcase and doc updates too! Due to some security requirements we have, all our projects require signed commits. Do you mind re-pushing your commits with signatures? If you don't want to do that, I can re-create your changes and merge. The downside is that you won't get "credit" for the commits.

[mdlavin]

@BerkliumBirb P.S. after I approved the automation run, I see that it failed with a missing reference

[BerkliumBirb]

• Signed commits with GPG signature
• Added abortcontroller-polyfill, because I failed to find the way to pass --experimental-abortcontroller to Node for testing or find any more reputable polyfill from core-js for example.
• Fixed doc entry

[mdlavin]

I appreciate the time you put into this. The need to add a polyfill for tests concerns me a little bit.

Does the addition of AbortSignal bump up the Node.js requirements to >= v16? If so, we should mark the change as a breaking change. I can push a new commit to this branch to do that.

[BerkliumBirb]

AbortController is marked as implemented from v14.17.0. In v14.17.0+ it can be used under experimental flag. I tried to pass experimental flag through nyc to not bring any polyfills, but wasn't able to.

This polyfill is only used in tests, and the actual code doesn't use anything global. We can ditch the whole AbortController/AbortSignal stuff and use { aborted: boolean } as AbortSignal in tests instead and remove any polyfills, but I don't know if it's a good idea to trim API down to the only used field.

I also don't really think this feature deserves a major bump, but if you think it does, we can go that way.

So, we have 4 options:

1. Try to pass --experimental-abortcontroller through nyc. I need help with this one.
2. Use dummy { aborted: boolean } as AbortSignal instead of the actual Controller/Signal.
3. Bump major to require node v16
4. Use polyfill

Which one should we go?