elm widget: move some types used in elm_widget.eo to Eolian files

elm widget: move some types used in elm_widget.eo to Eolian files

Move declarations of types used in elm_widget.eo to elm_general.eot and
elm_widget.eo.
Give them a Eolian name and use it instead of the old ones.

Correct the type name of some other types used as method parameters, by
using the Eolian names instead of legacy/generated names.

Reorganize the positions of elm_widget.eo.h inclusion and
of callback type declarations in elm_widget.h.
This make a clearer distinction of the types in elm_widget.h that are
still required in elm_widget.eo.h.