efl_ui_spotlight: do not inherit from layout anymore
before we inherited from layout, however the theme of the layout was
basically just the event part, and the holder part for the indicator.
The indicator part is going to be refactored into something else
anyways, since the indicator should be useable on other widgets as well.
Which means, only the event part is left, which is only used by the
scroller spotlight manager, (and now moved there).
With the move from this away we are saving round about 0.2KB of pure
edje accounting. Additionally, we are saving in perf 4% that is spend in
_efl_canvas_layout_efl_gfx_entity_size_set, which also makes this less
CPU intensive when resizing (Or even just starting is also enough).
Differential Revision: https://phab.enlightenment.org/D10765