Bug 1784772 - Queue SwipeEventQueue only if we don't know whether the pan event wasn...

Bug 1784772 - Queue SwipeEventQueue only if we don't know whether the pan event wasn't consumed by APZ. r=botond

If we queue the SwipeEventQueue in the case where the corresponding pan-start
event was consumed by the root content APZC, we wait for a response from the
content. And if the consumed pan-start event scrolled to the edge of the scroll
container and if the new scrolled position has been reached to the content
process before we tell whether the scroll position of the scroll container is
at the edge [1], we report it back to the SwipeTracker as the event should be
an event as a start of swipe navigation gestures. Thus, once after we got a
pan-end event, we trigger a swipe navigation. It results timeouts on a test case
waiting for an APZ:TransformEnd notification which never happens due to the page
navigation.

There's also a similar race condition where a pan-start event was consumed by a
non-root content APZC. But I haven't been able to reproduce the similar case
manually so I just filed bug 1821967 for the race and I am not going to handle
the race here. Note that I haven't been able to reproduce the original race
condition manually either though.

[1] https://searchfox.org/mozilla-central/rev/2f9a79d1c4ae7090cf50d93be86ba9dc2767a733/dom/events/EventStateManager.cpp#3727-3728

Differential Revision: https://phabricator.services.mozilla.com/D172391