This solves two issues. First, it's more correct, the indexers should be live.
Second, it makes sure that anything with an HTMLCollection prototype, like
HTMLOptionsCollection, also gets access to the index getters.
We could solve the 2nd issue by making `postAttach` work up the prototype
chain, but since postAttach is wrong (not live), I prefer this solution.
Allows dynamic imports to be loading asynchronously. I know reddit isnt the
best example, since it doesn't fully load, but this reduced the load time from
~7.2s to ~4.8s.
The first time a `slotchange` event is registered, we setup a SlotChangeMonitor
on the page. This uses a global (ugh) MutationEvent to detect slot changes.
We could improve the perfomance of this by installing a MutationEvent per
custom element, but a global is obviously a lot easier.
Our MutationEvent currently fired _during_ the changes. This is problematic
(in general, but specifically for slotchange). You can image something like:
```
slot.addEventListener('slotchange', () => {
// do something with slot.assignedNodes()
});
```
But, if we dispatch the `slotchange` during the MutationEvent, assignedNodes
will return old nodes. So, our SlotChangeMonitor uses the page scheduler to
schedule dispatches on the next tick.
Refactors some of the module loading logic. Both normal modules import and
dynamic module import now share more of the same code - they both go through
the slightly modified `module` function.
Dynamic modules now check the cache first, before loading, and when cached,
resolve the correct promise. This can now happen regardless of the module
loading state.
Also tried to replace some page arenas with call arenas and added some basic
tests for both normal and dynamic module loading.
According to MDN, inline script tags should not have defer/async attributes. But
some do. This ignores those attributes for inline script tags.
(Previously, we were only half ignoring them. We were treating them as inline,
but flagging them as deferred or async, which was causing issues with cleanup)
Fixes: https://github.com/lightpanda-io/browser/issues/1014
