Threading service updated to rely on spring rather than context code

I would like to remove the threading service eventually. It seems to just keep track of threads it creates using weak references, but the threads in the set are seemingly never fetched?
Right, I was going to do that entire class next (and separately). That way I can remove all of the qualifiers at once. In fact, I think we can delete this file and put the appropriate logic in `PowerProxyEventManager`.