Plot outputs incorrectly sized inside scaled outputs

[jcheng5]

Fixes #4135.

CSS zoom property affects el.getBoundingClientRect() but not el.offsetWidth/Height. When reporting sizes of outputs from client to server, we need to back out the CSS zoom because those sizes are used as CSS width/height, which will be affected by zoom.

(Note that something similar happens with CSS transforms but we don't have a good way to deal with them)

Safari doesn't support el.currentCSSZoom, but it also doesn't have the problem of el.getBoundingClientRect() and offset size not matching when zoom is applied. We're hoping that these two facts are not a coincidence and that any browser that treats those sizes as different also gives us el.currentCSSZoom.

getBoundingClientRect is also used in the coordmap for plots. @gadenbuie and I verified that coordmaps already work well even when zoom is applied. The coords_css uses el.getBoundingClientRect() without backing out the zoom; I'm convinced this is correct/how it has to be.

[gadenbuie]

LGTM! It seems that currentCSSZoom will be available when we update typescript to >= 5.5.2.

[gadenbuie]

currentCSSZoom was added in typescript release 5.5.2 (here's the commit); worth adding a TODO and hope we catch this in the future.

Suggested change

	// Cast to any because currentCSSZoom isn't in the type def of HTMLElement
	const zoom = (el as any).currentCSSZoom || 1;
	// Cast to any because currentCSSZoom isn't in the type def of HTMLElement
	// TODO: typescript >= 5.5.2 added this property to the type definition
	const zoom = (el as any).currentCSSZoom || 1;