Debugger: Use a QStringView for debugview into output buffer

This is unused unless debugging creator itself.

Change-Id: Ic30fe4970c4b0ec79e977ef932d0516ab1ba0792
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/debugger/debuggerprotocol.h

@@ -118,7 +118,7 @@ public:
     QString readCString();
     QString readString(const std::function<bool(char)> &isValidChar);
 
-    QString buffer() const { return QString(from, to - from); }
+    QStringView buffer() const { return QStringView(from, to - from); }
     int remainingChars() const { return int(to - from); }
 
     void skipCommas();