Making the k6/experimental/timers module part of the k6 core

[mstoykov]

xk6-timers implement the very old setTimeout and co.

The module has a single open issue grafana/xk6-timers#3 and is used fairly commonly.

The functionality it provides is also needed to delay execution in ways similar to sleep but without blocking the event loop.

Blockers:

1. setTimeout does not fire in order xk6-timers#3 - the issue should be fixed.
2. what will be the import path k6/timers ? Do we want to actually just have it globally, given how it is usually used in JS. That will add more intercompatibility with other JS engines.

Alternatives:

While setTimeout and co are very old and known, they are not very promise/async/await friendly as they predate them.

The things that keeps poping out is delay both from

1. deno std lib
2. npm package
3. a gist with a version for k6

The provided APU has the benefit of doing

// code A
await delay(10);
// code B

instead of

// code A
setTimeout( () => {
  // code B
}, 10)

But likely we should still have setTimeout and co.

[codebien]

Feature request for having setTimeout as global #3329