[aurorae] fix incorrectly disabled blur for maximized windows

when aurorae decorated windows become maximized and back to normal, after a while they all start to disable blur for their decorated maximized windows.

- bug was tracked down to aurorae fault sending empty QRegions for its maximized windows. What probably happens is that because mask FrameSvgItem enabled borders change from AllBorders to NoBorder, mask FrameSvgItem calculations can not catch up
- the new approach is lighter than the previous one and simpler as margins and enabledborders for mask framesvgitem are not changed and in the c++ side no QRegions calculations are needed at all for maximized windows
- in my system with the new code changing from normal window to maximized one feels a bit snapper