Clear existing timeouts when an abort signal aborts

[ronami]

Summary

Currently, running the following code would show the error being logged, but the process would only exist after 5 seconds (the value being passed as milliseconds):

import pTimeout from "p-timeout";

const promise = new Promise(() => {});
const abortController = new AbortController();

const p = pTimeout(promise, {
	milliseconds: 5000,
	signal: abortController.signal,
});

p.then(() => console.log("done")).catch((e) => console.log("error", e));

setTimeout(() => {
	abortController.abort();
}, 1000);

This happens because the setTimeout call (see here) isn't cleared when a signal has been passed and then aborted. This ongoing timeout can cause Node to hang until it's finished (if it's the only thing holding it from closing).

This PR fixes this by cleaning up the timers not only after the promise has finished, but after p-timeout's own promise finishes, which includes possibly rejecting because of an abort signal.

[ronami]

The main branch is currently red on what seems like an unrelated issue, see #37.