Use Utils::FutureSynchronizer in IosSimulatorToolHandlerPrivate

Add a new method: void FutureSynchronizer::cancelAllFutures().

Change-Id: I5a4e1ea3230ac3c0ce9d3f26b751b2c05fe3dfd4
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/libs/utils/futuresynchronizer.h

@@ -49,6 +49,7 @@ public:
     bool isEmpty() const;
 
     void waitForFinished();
+    void cancelAllFutures();
     void clearFutures();
 
     void setCancelOnWait(bool enabled);