focus: do not allow focus to exit a popup

focus: do not allow focus to exit a popup

Summary:
Popup windows dim the background and do not allow the user
to click outside the popup. However, pressing TAB can take
you to widgets on the background. This didn't happen in
legacy.

Fixes T7432

Test Plan: Instructions in T7432

Reviewers: bu5hm4n, stephenmhouston, Jaehyun_Cho, herb, Blackmole, zmike

Reviewed By: zmike

Subscribers: zmike, felipealmeida, lauromoura, cedric, #reviewers, #committers

Tags: #efl

Maniphest Tasks: T7432

Differential Revision: https://phab.enlightenment.org/D7171