LibGUI: Add DynamicWidgetContainter

Add a new widget "DynamicWidgetContainer" that is used to group it's
child widgets within an collapsable and detachable container. The
DynmnicWidgetContainer is able to persist it's view state if a config
domain has been provided. Having that set will allow the widget to
restore it's view state automatically.

Userland/Libraries/LibGUI/DynamicWidgetContainerControls.h

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2023, Torsten Engelmann <engelTorsten@gmx.de>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibGUI/Button.h>
+#include <LibGUI/Frame.h>
+#include <LibGUI/LabelWithEventDispatcher.h>
+
+namespace GUI {
+
+class DynamicWidgetContainerControls : public GUI::Widget {
+    C_OBJECT_ABSTRACT(DynamicWidgetContainerControls)
+public:
+    static ErrorOr<NonnullRefPtr<DynamicWidgetContainerControls>> try_create();
+    virtual ~DynamicWidgetContainerControls() override = default;
+
+    RefPtr<GUI::Button> get_collapse_button()
+    {
+        return find_descendant_of_type_named<GUI::Button>("collapse_button");
+    }
+
+    RefPtr<GUI::Button> get_expand_button()
+    {
+        return find_descendant_of_type_named<GUI::Button>("expand_button");
+    }
+
+    RefPtr<GUI::Button> get_detach_button()
+    {
+        return find_descendant_of_type_named<GUI::Button>("detach_button");
+    }
+
+    RefPtr<GUI::LabelWithEventDispatcher> get_event_dispatcher()
+    {
+        return find_descendant_of_type_named<GUI::LabelWithEventDispatcher>("section_label");
+    }
+
+private:
+    DynamicWidgetContainerControls() = default;
+};
+
+}