Move InfoBar to Utils

The only reason it was required to be in Core plugin, was its use of Id,
which now is available in Utils.

Change-Id: I66ce863c24924e6448d339b3422538a7fe167336
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/coreplugin/icore.cpp

@@ -654,7 +654,7 @@ QStatusBar *ICore::statusBar()
     Use for notifying the user of something without interrupting with
     dialog. Use sparingly.
 */
-InfoBar *ICore::infoBar()
+Utils::InfoBar *ICore::infoBar()
 {
     return m_mainwindow->infoBar();
 }