Debugger: Re-enable watchers after ending a debugger run

In that state one should be able to remove them.

Change-Id: I9c1383decb087971cdc01607c32801f6ac22f99d
Reviewed-by: Christian Stenger <christian.stenger@theqtcompany.com>

src/plugins/debugger/watchhandler.h

@@ -244,6 +244,7 @@ public:
     void removeItemByIName(const QByteArray &iname);
     void removeAllData(bool includeInspectData = false);
     void resetValueCache();
+    void resetWatchers();
     void notifyUpdateStarted();
     void notifyUpdateFinished();
     void purgeOutdatedItems(const QSet<QByteArray> &inames);