This allows overlays to request draw after any interface or layer. This
allows removal of the ABOVE_MAP layer which can now just be replaced
with requesting draw after the map interface. This also fixes item
overlays from drawing over top of the map by now drawing the item
overlay immediately after the interface and/or layer the item is on is
drawn.
For backwards compatability, ABOVE_WIDGETS is kept as a layer, but
internally just requests draw after the 3 TLIs.
Due to overlays defaulting to the UNDER_WIDGETS layer, a new layer
MANUAL has been added, which is intended for use when requesting draw
after specific interfaces or layers, so that the overlay is otherwise
not drawn a second time due to being UNDER_WIDGETS.
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