Backport Navigation (and friends)

[mookums]

This backports Navigation mostly and all of the related changes that I made across various PRs.

This backports a number of PRs (including various with zigdom_backport labels)

• Implement History WebAPI. #1086
• add Navigation WebAPI #1138
• Fix build issues related to Navigation #1182
• Update wpt submodule for Navigation #1192
• add set_hash to Location #1200
• Run microtasks before onload #1206
• add PageTransitionEvent #1207
• Assorted Navigation Changes/Fixes #1215

This also brings over the URL stitch (now resolve) fix and the regression test that was solved by #1113.

[karlseguin]

Wasn't expecting that...Is there a reason for having these onRemovePage and onNewPage at all? Can the Navigation instance not be created once (in the Session)...nothing here references the *Page or anything tied to the page lifetime (e.g. window) as far as I can see.

[mookums]

The Navigation has an EventTarget so with libdom, we had to create a new EventTarget whenever a new Page was created (or we'd get a segfault). With zigdom (from my understanding), since we create a new Factory whenever we get a new page, we need to create a new EventTarget for it whenever we create a new page.

[karlseguin]

It can be created outside the factory, or the factory methods could take an opts that allows an explicit allocator to be passed in (though I don't love that approach, since it's an if check on every create).

[karlseguin]

This looks good. Up to you if you think it's worth moving the Navigation instance to the session-owned arena so that we don't to reset between page navigation events - but I do think it would be cleaner. I'm trying to think if there are any implications to doing it (since nothing else does)...can't think of any.