The use of "Endpoint" vs "Endpoints" in these type names is tricky
because it doesn't always make sense to use the same singular/plural
convention as the corresonding service-related types, since often the
service-related type is referring to a single service while the
endpoint-related type is referring to multiple endpoint IPs.
The "endpointsInfo" types in the iptables and winkernel proxiers are
now "endpointInfo" because they describe a single endpoint IP (and
wrap proxy.BaseEndpointInfo).
"UpdateEndpointMapResult" is now "UpdateEndpointsMapResult", because
it is the result of EndpointsMap.Update (and it's clearly correct for
EndpointsMap to have plural "Endpoints" because it's a map to an array
of proxy.Endpoint objects.)
"EndpointChangeTracker" is now "EndpointsChangeTracker" because it
tracks changes to the full set of endpoints for a particular service
(and the new name matches the existing "endpointsChange" type and
"Proxier.endpointsChanges" fields.)
