Fix tracking of geometry restore with electric maximize

If the user wants to move a tiled window, but changes their mind and
tiles the window back to the previous position, the geometryRestore()
will be corrupted because initialMoveResizeGeometry() is the same as the
geometry of the window in the tiled mode.

This change fixes tracking of the geometry restore by precomputing the
geometry restore when starting interactive move. That way, if the window
is untiled and tiled again without release left pointer button, the
geometry restore will be set to the correct value in setQuickTileMode().

This change also adjusts the test suite so such a subtle case won't be
broken again without noticing it.


(cherry picked from commit 77f712d3)