Reduce usage of app_version header

Most information is available via Q(Core|Gui)Application.
Add an AppInfo structure for the things that are not.

This avoids that the information ends up duplicated and
hardcoded in the plugins, which is not needed or desired.

Change-Id: I4d565e75c42a7b8facafa90c27096ea49359215d
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/plugins/coreplugin/icore.h

@@ -80,8 +80,6 @@ public:
     static Utils::FilePath libexecPath(const QString &rel = {});
     static Utils::FilePath crashReportsPath();
 
-    static QString ideDisplayName();
-
     static QString versionString();
 
     static QMainWindow *mainWindow();