[WidgetControl.Manual][Non-ACR] Fix WidgetViewerApp
Due to the discontinuation of EFL support in Tizen 7.0,
the EFL-based WidgetViewer that worked properly in previous versions was not functioning correctly.
This patch resolves the issue by redeveloping the WidgetViewer app using NUI.
Note that WidgetBaseApp is still implemented based on EFL, which may cause UI update issues.
When testing on a TV, please connect a mouse to perform the test.
Change-Id: Iff9a38783929e55faaf91b12563c60dc43ac1783
Signed-off-by: Changgyu Choi <changyu.choi@samsung.com>