Better distinguish the two kinds of proxy health check servers

Kube-proxy runs two different health servers; one for monitoring the
health of kube-proxy itself, and one for monitoring the health of
specific services. Rename them to "ProxierHealthServer" and
"ServiceHealthServer" to make this clearer, and do a bit of API
cleanup too.

pkg/proxy/iptables/proxier_test.go

@@ -35,6 +35,7 @@ import (
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/apimachinery/pkg/util/intstr"
 	"k8s.io/kubernetes/pkg/proxy"
+	"k8s.io/kubernetes/pkg/proxy/healthcheck"
 	utilproxy "k8s.io/kubernetes/pkg/proxy/util"
 	utilproxytest "k8s.io/kubernetes/pkg/proxy/util/testing"
 	"k8s.io/kubernetes/pkg/util/async"
@@ -342,28 +343,6 @@ func (f *fakePortOpener) OpenLocalPort(lp *utilproxy.LocalPort) (utilproxy.Close
 	return nil, nil
 }
 
-type fakeHealthChecker struct {
-	services  map[types.NamespacedName]uint16
-	endpoints map[types.NamespacedName]int
-}
-
-func newFakeHealthChecker() *fakeHealthChecker {
-	return &fakeHealthChecker{
-		services:  map[types.NamespacedName]uint16{},
-		endpoints: map[types.NamespacedName]int{},
-	}
-}
-
-func (fake *fakeHealthChecker) SyncServices(newServices map[types.NamespacedName]uint16) error {
-	fake.services = newServices
-	return nil
-}
-
-func (fake *fakeHealthChecker) SyncEndpoints(newEndpoints map[types.NamespacedName]int) error {
-	fake.endpoints = newEndpoints
-	return nil
-}
-
 const testHostname = "test-hostname"
 
 func NewFakeProxier(ipt utiliptables.Interface, endpointSlicesEnabled bool) *Proxier {
@@ -380,7 +359,7 @@ func NewFakeProxier(ipt utiliptables.Interface, endpointSlicesEnabled bool) *Pro
 		hostname:                 testHostname,
 		portsMap:                 make(map[utilproxy.LocalPort]utilproxy.Closeable),
 		portMapper:               &fakePortOpener{[]*utilproxy.LocalPort{}},
-		healthChecker:            newFakeHealthChecker(),
+		serviceHealthServer:      healthcheck.NewFakeServiceHealthServer(),
 		precomputedProbabilities: make([]string, 0, 1001),
 		iptablesData:             bytes.NewBuffer(nil),
 		existingFilterChainsData: bytes.NewBuffer(nil),