Introduce MultiCIDRRangeAllocator

MultiCIDRRangeAllocator is a new Range Allocator which makes using
multiple ClusterCIDRs possible. It consists of two controllers, one for
reconciling the ClusterCIDR API objects and the other for allocating
Pod CIDRs to the nodes.

The allocation is based on the rules defined in
https://github.com/kubernetes/enhancements/tree/master/keps/sig-network/2593-multiple-cluster-cidrs

test/integration/ipamperf/ipam_test.go

@@ -50,8 +50,10 @@ func setupAllocator(kubeConfig *restclient.Config, config *Config, clusterCIDR,
 
 	sharedInformer := informers.NewSharedInformerFactory(clientSet, 1*time.Hour)
 	ipamController, err := nodeipam.NewNodeIpamController(
-		sharedInformer.Core().V1().Nodes(), config.Cloud, clientSet,
-		[]*net.IPNet{clusterCIDR}, serviceCIDR, nil, []int{subnetMaskSize}, config.AllocatorType,
+		sharedInformer.Core().V1().Nodes(),
+		sharedInformer.Networking().V1alpha1().ClusterCIDRs(),
+		config.Cloud, clientSet, []*net.IPNet{clusterCIDR}, serviceCIDR, nil,
+		[]int{subnetMaskSize}, config.AllocatorType,
 	)
 	if err != nil {
 		return nil, shutdownFunc, err