Data structure to hold RegionInfo and the address for the hosting HRegionServer. Immutable.
Comparable, but we compare the 'location' only: i.e. the hostname and port, and *not* the
regioninfo. This means two instances are the same if they refer to the same 'location' (the same
hostname and port), though they may be carrying different regions. On a big cluster, each client
will have thousands of instances of this object, often 100 000 of them if not million. It's
important to keep the object size as small as possible.
This interface has been marked InterfaceAudience.Public in 0.96 and 0.98.