TaskTree: Prepare for de-utils-ization - part 2

Move TaskTree into Tasking namespace.
Move Tasking namespace out of Utils namespace.

Change-Id: Ib4c1d7f54f1808517e54768dfa27209c33517b61
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: hjk <hjk@qt.io>

src/plugins/projectexplorer/abstractprocessstep.cpp

@@ -20,6 +20,7 @@
 #include <algorithm>
 #include <memory>
 
+using namespace Tasking;
 using namespace Utils;
 
 namespace ProjectExplorer {
@@ -240,7 +241,7 @@ void AbstractProcessStep::setupProcess(Process *process)
     });
 }
 
-void AbstractProcessStep::runTaskTree(const Tasking::Group &recipe)
+void AbstractProcessStep::runTaskTree(const Group &recipe)
 {
     setupStreams();