elm: Remove range "span_size" API in EO

elm: Remove range "span_size" API in EO

Reasons:
 - This API has been confused with the min size of the widget, resulting
   in badly laid out applications.
 - The EO API was not very nice (Range is about numbers, the Gfx size
   hint in a part is really ugly).

While I understand the value of this API and how it can be used in
scalable applications, it is in fact not absolutely necessary.
Alternatively to that span size, the widget min size can already be
defined from the application side, or the widget can simply be expanded
to fill in its parent.

This can obviously be reinstated later if the need arises for EO. For
now, keep this feature as legacy-only.