Just check that the actual IP:port of the filtered endpoints is
correct; using DeepEqual requires us to copy all the extra endpoint
fields (eg, ZoneHints, IsLocal) from endpoints to expectedEndpoints,
which just makes the test cases unnecessarily bigger.
The "node local endpoints, hints are ignored" test was not actually
enabling topology correctly, so it would have gotten the expected
result even if the code was wrong. (Which, FTR, it wasn't.)
1. Add API definitions;
2. Add feature gate and drops the field when feature gate is not on;
3. Set default values for the field;
4. Add API Validation
5. add kube-proxy iptables and ipvs implementations
6. add tests
