An SbcResource is some sort of entity that can be waited on in the BalancerResourceManager
and which works with the SbcEventQueue.
See SbcResources for examples of resource types.
Return a hash value for this SbcResource.
Note that this implementation of SbcResources will treat resources of the same underlying type as equivalent; i.e. an SbcResource<Integer> hashes
identical to another SbcResource<Integer>.