efl_ui/table: optimize position_set operations with tables

efl_ui/table: optimize position_set operations with tables

if a table is moved and no other changes are made to the table or its children,
e.g., if the table is scrolled, then there is no need to loop over the table's
items repeatedly in order to accurately calculate all the item geometries
and positions.

instead, simply apply an offset from the last table calc position to each child
item and handle the position changes more transparently

this yields roughly a 12% perf improvement to the 'efl.ui.scroller simple2' test
and brings rendering up to nearly 60fps

Reviewed-by: Cedric BAIL <cedric.bail@free.fr>
Differential Revision: https://phab.enlightenment.org/D9346