TaskTree: Unify TaskInterface::done(DoneResult) signal

Change the argument of TaskInterface::done() signal
from bool into DoneResult. Make it consistent with
other TaskTree API.

Introduce toDoneResult(bool success) helper.

Change-Id: I7b3041d7c1ed0317c76adbc1fd37448231e85f82
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: hjk <hjk@qt.io>

src/plugins/languageclient/currentdocumentsymbolsrequest.h

@@ -30,7 +30,7 @@ public:
     CurrentDocumentSymbolsData currentDocumentSymbolsData() const { return m_currentDocumentSymbolsData; }
 
 signals:
-    void done(bool success);
+    void done(Tasking::DoneResult result);
 
 private:
     void clearConnections();