Calling the `Drop` impl of the user's `ApplicationHandler` is important on
iOS and Web, since they don't return from `EventLoop::run_app`.
And now that we reliably call `Drop`, the `ApplicationHandler::exited`
event/callback is unnecessary; using `Drop` composes much better (open files
etc. stored in the app state will be automatically flushed), and prevents
weirdness like attempting to create a new window while exiting.
* Fix a pause in the event loop when clicking the title bar on windows
When clicking the title bar on Windows, to drag the window, there is
a noticible pause in continuous redraw requests. This was fixed
in #839 and then regressed in #1852. The cursor blinks in both
cases and is unrelated. The regression made the blink happen after
the pause instead of immediately.
* Update the event loop pause note on the WM_NCLBUTTONDOWN handler
The application example was also updated to optionally animate the fill color
in order to demonstrate continuous redraw without pauses in the event
loop.
This also alters `VideoMode` to be a regular object and not reference
the `MonitorHandle`, since it's a static data.
Given that `VideoMode` set may change during runtime keeping the
reference as a some sort of validity may not be idea and propagating
errors when changing video mode could be more reliable.
