Summary:
This commit includes follwoing works.
1. change parent class from EFL_UI_SLIDER_INTERVAL
to EFL_UI_LAYOUT_BASE
2. get all necessary codes from efl_ui_slider and
efl_ui_slider_interval to elm_slider
3. add callbacks to slider test code
ref T7893
Test Plan:
1. elementary_test
2. slider
3. operate sliders on the window
Reviewers: bu5hm4n, segfaultxavi, eagleeye, zmike
Reviewed By: zmike
Subscribers: zmike, cedric, #reviewers, #committers
Tags: #efl
Maniphest Tasks: T7893
Differential Revision: https://phab.enlightenment.org/D9623
ebae12f06a