TaskTree: Get rid of registration macros

Alias task types manually.
Don't require the alias to be inside the Tasking namespace.
Addresses the 22th point of the jira ticket below.

Task-number: QTCREATORBUG-28741
Change-Id: I1bdda7fe5a01e4bcb5052ec328f4e0eace878651
Reviewed-by: hjk <hjk@qt.io>

src/plugins/android/androiddeployqtstep.cpp

@@ -565,7 +565,7 @@ Tasking::GroupItem AndroidDeployQtStep::runRecipe()
         async.setConcurrentCallData(&AndroidDeployQtStep::runImpl, this);
         async.setFutureSynchronizer(&m_synchronizer);
     };
-    return Tasking::AsyncTask<void>(onSetup);
+    return AsyncTask<void>(onSetup);
 }
 
 void AndroidDeployQtStep::runCommand(const CommandLine &command)