Utils: Add push button with menu and default click action

QPushButton has the functionality of setting a menu, but that replaces
the normal "click" functionality, and always opens the menu on click.

QToolButton can have a menu and the user can still click on it to just
click. But, QToolButton looks very different, and in combination with
other, normal push buttons very alien.

Create a push button that only shows the menu when clicking on/near the
menu indicator, and otherwise just sends the clicked() signal like a
non-menu push button.

Change-Id: Id6ba367e40c370275f67f0fbf77521c2e974b3b8
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Marcus Tillmanns <marcus.tillmanns@qt.io>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/libs/utils/optionpushbutton.h

@@ -0,0 +1,31 @@
+// Copyright (C) 2022 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0 WITH Qt-GPL-exception-1.0
+
+#pragma once
+
+#include "utils_global.h"
+
+#include <QPushButton>
+
+QT_BEGIN_NAMESPACE
+class QMenu;
+class QMouseEvent;
+QT_END_NAMESPACE
+
+namespace Utils {
+
+class QTCREATOR_UTILS_EXPORT OptionPushButton : public QPushButton
+{
+    Q_OBJECT
+
+public:
+    OptionPushButton(QWidget *parent = nullptr);
+    OptionPushButton(const QString &text, QWidget *parent = nullptr);
+
+    void setOptionalMenu(QMenu *menu);
+
+protected:
+    void mouseReleaseEvent(QMouseEvent *event) override;
+};
+
+} // namespace Utils