elm_datetime, efl_ui_clock : Add check 'legacy widget' for layout signal emission

elm_datetime, efl_ui_clock : Add check 'legacy widget' for layout signal emission

Summary:
08a11d, Signal name is changed to efl ui signal name
legacy widget should use elm
This commit resolves T6928

#efl, #regression

Test Plan: elementary_test -to datetime

Reviewers: JackDanielZ, Jaehyun_Cho, Hermet, YOhoho, devilhorns, zmike

Reviewed By: zmike

Subscribers: YOhoho, cedric, Hermet, Jaehyun_Cho, #committers, JackDanielZ, zmike

Tags: #efl

Maniphest Tasks: T6928

Differential Revision: https://phab.enlightenment.org/D6289