Reuse single instance of ResizeObserver in Flyouts.

[mareksed]

Is your feature request related to a problem? Please describe.
Our use case in which we are using reshaped is performance sensitive.
My knowledge about ResizeObservers is that less instances we have the better the perf is,
please follow this thread WICG/resize-observer#59 (comment)

I found this snippet in sources of useFlyout.

	React.useEffect(() => {
		const resizeObserver = new ResizeObserver(() => updatePosition({ sync: true }));

		resizeObserver.observe(document.body);
		if (triggerElRef.current) resizeObserver.observe(triggerElRef.current);

		return () => resizeObserver.disconnect();
	}, [updatePosition, triggerElRef]);

useFlyout is a hook that is composed a lot, and is at the core of every Tooltip, so it will be used a lot in an UI and will create, new ResizeObserver and every one of those will be observing document body.

Describe the solution you'd like
Reuse single instance of ResizeObserver