There was a line of CSS that set pointer-events: none on widget
iframes whilst they were being resized to stop iframes swallowing
the mousemove/up events while dragging the resize handle, but a)
all widgets are now in a persisted element wrapper and therefore
not in the right place in the DOM to get that CSS and b) that only
got set when resizing the whole aps drawer vertically, not dragging
the handle between apps to change the width distribution.
Add a pointer events prop to AppTile to allow the pointer-events
style to be set by the parent, and set it when dragging either
resize handle.
Fixes https://github.com/vector-im/element-web/issues/16473