Problem: Cluster scoped gc was taking significantly longer to complete
than before 7387aa5. This was due to a large number of list calls and
the time needed to iterate over them.
Solution: Instead of requesting every type than Rancher uses, a
seperate map appended to when a cluster scoped handler
is created. The full map of all GroupVersionResources is kept as a
fallback for the use case where user controllers may exist on another
host other than the current leader.
Problem: Cluster scoped handlers were not being cleaned up without
manually writing garbage collection functions.
Solution: All cluster scoped handlers will be recorded in a global map
in a generic format so that they can be removed by a generic function.
