Utils: More forward declarations / drop unused headers [D-G]

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

Change-Id: Id42cd7b3743a816f75cecb6b576c0e37cb057473
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: hjk <hjk@qt.io>

src/plugins/android/javalanguageserver.cpp

@@ -44,6 +44,7 @@
 
 #include <QGridLayout>
 #include <QLineEdit>
+#include <QXmlStreamWriter>
 
 using namespace ProjectExplorer;
 using namespace Utils;