[Impeller] new blur: expand coverage clip to work for rotated entities #140890
Description
Spawned from flutter/engine#49299
We landed that optimization just for translation and scaling transforms to capture backdrop filters. It wasn't working with rotation. It's lower priority but would be ideal that the optimization works for that as well, just drawing the uv's for the AABB that contains the rotated entity.
See Brandon's comment here: flutter/engine#49299 (comment)