Utils: More forward declarations / drop unused headers [H-K]

Round 1 - focus on headers.
For classes with initial in range [H-K].
Try to keep the same separators between different kind of headers.

Change-Id: Iefb032953743be41a847ee011c30527edfa425d8
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/plugins/todo/todoicons.cpp

@@ -23,12 +23,13 @@
 ** be met: https://www.gnu.org/licenses/gpl-3.0.html.
 **
 ****************************************************************************/
+
+#include "todoicons.h"
+
 #include <utils/icon.h>
 #include <utils/theme/theme.h>
 #include <utils/utilsicons.h>
 
-#include "todoicons.h"
-
 using namespace Utils;
 
 namespace Todo {