The code was assuming that if an Endpoint got moved from one slice to
another, and one is "local" but the other isn't, then we should prefer
the local one. But this doesn't make sense; if it's actually the same
Endpoint (i.e., same targetRef) then both copies will have the same
Hostname. And if it's not the same Endpoint, then one of the two
Endpoints is wrong, but there's no reason to assume it's the non-local
one.
newFakeProxier was inlining the details of NewEndpointsChangeTracker
so it could override trackerStartTime, but it would be better and more
future-proof to just call NewEndpointsChangeTracker normally and then
edit that one field.
(Also remove an unused FakeProxier field.)
EndpointSliceCache was using the name "endpointInfo" to refer to two
different data types (most egregiously in addEndpoints(), which had a
variable named `endpoint` of type `*endpointInfo` and a variable named
`endpointInfo` of type `Endpoint`).
Continue using "endpointInfo" in places that refer to proxy.Endpoint /
BaseEndpointInfo, since that's consistent with other code, but rename
the local "cache of the Endpoints field of an EndpointSlice" type from
"endpointInfo" to "endpointData". Likewise, rename endpointSliceInfo
to endpointSliceData, for consistency.
Move the ServicePort/BaseServicePortInfo types to serviceport.go.
Move the Endpoint/BaseEndpointInfo types to endpoint.go.
To avoid confusion with the new filenames, rename service.go to
servicechangetracker.go and endpoints.go to endpointschangetracker.go.
(No code changes; this just moves some code from types.go and
services.go to serviceport.go, and some code from types.go and
endpoints.go to endpoint.go.)
