helgrind support

I wanted to suggest to support in the future the helgrind tool from valgrind in the debugger. This was already asked some time ago in the forum but I couldn't find any associated feature request. https://forum.qt.io/topic/62726/calling-helgrind-in-qt-creator

Right now, I use the workaround:

valgrind -xml=yes --xml-file=helgrind.xml -suppressions=some-helgrind.supp --log-file=helgrind.log myTarget.exe

and then go to the QtCreator debugger and click on "load external XML file". This works fine, but it is a bit of a workaround. It would be nice if it could be done directly. Right now, only "valgrind Memcheck and callgrind" is possible.