efl_ui_text: apply new theme logic and use constructor/destructor
Summary:
It removes legacy aliases from efl_ui_text's theme.
And it also move all code from group add/del overriding functions to
constructor/destructor.
@fix
Test Plan: N/A
Reviewers: jpeg, taxi2se
Subscribers: cedric
Differential Revision: https://phab.enlightenment.org/D5601