Fix rectangle screenshots with less than 100% UI scale

Noah Davis requested to merge work/ndavis/lessthan100 into master

Fixes it by just doing a normal all screens grab instead of trying to get an image for each screen and then trying to position and scale them all correctly for the given platform. This should also be a bit more efficient.

Also lays some of the ground work for rectangle video recording by making SelectionEditor send a rectangle and export actions instead of an image and export actions.

BUG: 462860 BUG: 473888

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