entry: Create selection handles as lazily as possible
entry: Create selection handles as lazily as possible

Summary:
Moved the construction of selection handles to _update_selection_handler in order to
reduce the cost of construction of elm_entry little bit.

Reviewers: thiepha, Hermet, seoz, raster

CC: seoz, raster

Differential Revision: https://phab.enlightenment.org/D756

rvandegrift/elementary,FlorentRevest/Elementary,FlorentRevest/Elementary,tasn/elementary,FlorentRevest/Elementary,tasn/elementary,FlorentRevest/Elementary,rvandegrift/elementary,tasn/elementary,rvandegrift/elementary,rvandegrift/elementary,tasn/elementary,tasn/elementary