The EndpointSlice for masters was not created after enabling
EndpointSlice feature on a pre-existing cluster. This was because the
Endpoint object had been created and ReconcileEndpoints would skip
creating or updating it after EndpointSlice feature is enabled.
This patch ensures EndpointSlice is consistent with Endpoints after the
reconciler reconciles Endpoints even if Endpoints is unchanged. It also
avoids an update if the desired EndpointSlice matches the existing one.
This should fix a bug that could break masters when the EndpointSlice
feature gate was enabled. This was all tied to how the apiserver creates
and manages it's own services and endpoints (or in this case endpoint
slices). Consumers of endpoint slices also need to know about the
corresponding service. Previously we were trying to set an owner
reference here for this purpose, but that came with potential downsides
and increased complexity. This commit changes behavior of the apiserver
endpointslice integration to set the service name label instead of owner
references, and simplifies consumer logic to reference that (both are
set by the EndpointSlice controller).
Additionally, this should fix a bug with the EndpointSlice GenerateName
value that had previously been set with a "." as a suffix.
