DAP: Add displaying nested variables

Change-Id: I588dde7c0ef402fe8d6c9d43dc9f0183bfa2d733
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/dap/dapengine.h

@@ -9,6 +9,8 @@
 
 #include <QVariant>
 
+#include <queue>
+
 namespace Debugger::Internal {
 
 class DebuggerCommand;
@@ -126,6 +128,10 @@ private:
 
     int m_nextBreakpointId = 1;
     int m_currentThreadId = -1;
+
+    std::queue<std::pair<int, WatchItem *>> m_variablesReferenceQueue;
+    WatchItem *m_currentWatchItem = nullptr;
+    WatchItem *m_rootWatchItem = nullptr;
 };
 
 } // Debugger::Internal