Don't allow timeouts to be registered when shutting down

[karlseguin]

Currently, a timeout that sets a timeout can cause loop.run to block forever.

Also, cleanup URL stitch with leading './'. The resulting URL was valid, but since we use the URL as the module cache key, it's important to resolve various representations of the same URL in the same way.

[karlseguin]

Initial version of this didn't work well.

The goal is to prevent this type of code:

function logEvents() {
   send(events);
   setTimeout(logEvents, 3000);

From making loop.run() run forever.

However, simply preventing timeouts from being registered during "shutdown" can break pages. For example, our fetch.js does this:

onload: function() {
  // ...
  setTimeout(function() {
    resolve(new Response(body, options));
  }, 0);
}

Which means that something like:

fetch(request).then((res) => {.....});

may not work if onload is called during loop.run (because we'll ignore the timeout to resolve the promise).

In other words, some timeouts we want to ignore, and some we don't. But I don't think we can tell which is why so, for now, I just added a timeout.

[krichprollsch]

I guess we will like to set a user-facing option at some point.

[karlseguin]

If we take a param, it should get used/passed to:

browser/src/browser/html/window.zig

Line 220 in cb35b36

if (delay > 5000) {

I was thinking something a bit fancier. Accepting an arbitrary JS script, e.g. --eval "document.getElementbyId('comments')" which we run on every loop and, when it returns a truthy JS value, we exit.