Multiple NIC support

[brianlieberman]

/kind feature

What this PR does / why we need it:
This PR adds support for attaching multiple network interfaces to both AzureMachines as well as AzureMachinePools (VMSS), it also allows to specify one or more IPConfigs for those interfaces to pre-warm them with multiple IPs on each interface.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes kubernetes-sigs#2327

Special notes for your reviewer:

• [x ] squashed commits
• [x ] includes documentation
• [ x] adds unit tests

Release note:

Adds a new optional field for a slice of NetworkInterfaces for AzureMachines and AzureMachinePools to specify a list of NetworkInterfaces, the SubnetName each should be in, and a slice of optional IPConfigs for each interface if desire.

Example below create a machine template with two interfaces in different subnets, and five IPs on the node-subnet interface: 

apiVersion: infrastructure.cluster.x-k8s.io/v1beta1
kind: AzureMachineTemplate
metadata:
  name: capi-quickstart-control-plane
  namespace: default
spec:
  template:
    spec:
       networkInterfaces:
           - subnetName: control-plane-subnet
             acceleratedNetworking: false
           - subnetName: node-subnet
             acceleratedNetworking: true
             ipConfigs:
              - {}
              - {}
              - {}
              - {}
              - {}
      dataDisks:
      - diskSizeGB: 256
        lun: 0
        nameSuffix: etcddisk
      osDisk:
        diskSizeGB: 128
        osType: Linux
      sshPublicKey: ""
      vmSize: Standard_D2s_v3

[dthorsen]

@brianlieberman Some of the functions have modifications but no corresponding tests.

I am also getting some linter errors when running make lint

azure/types.go:23:2: Expected 'i', Found '"' at azure/types.go[line 23,col 2] (gci)
	"sigs.k8s.io/cluster-api-provider-azure/api/v1beta1"
	^
azure/types.go:24:2: ST1019(related information): other import of "sigs.k8s.io/cluster-api-provider-azure/api/v1beta1" (stylecheck)
	infrav1 "sigs.k8s.io/cluster-api-provider-azure/api/v1beta1"
	^
api/v1beta1/types.go:555:68: Comment should end in a period (godot)
// IP Configuration defines options to confiure a network interface
                                                                   ^
api/v1beta1/types.go:550:2: var-naming: struct field IpConfigs should be IPConfigs (revive)
	IpConfigs             []AzureIPConfig `json:"ipConfigs,omitempty"`
	^
api/v1beta1/types.go:552:2: var-naming: struct field Id should be ID (revive)
	Id                    string          `json:"id,omitempty"`
	^
azure/scope/machine.go:223: unnecessary leading newline (whitespace)
func (m *MachineScope) NICSpecs() []azure.ResourceSpecGetter {

azure/services/networkinterfaces/spec.go:146:3: var-naming: var newIpConfigPropertiesFormat should be newIPConfigPropertiesFormat (revive)
		newIpConfigPropertiesFormat := &network.InterfaceIPConfigurationPropertiesFormat{}
		^
azure/services/scalesets/scalesets.go:486: File is not `gofmt`-ed with `-s` (gofmt)
					for j, _ := range n.IpConfigs {
exp/api/v1beta1/azuremachinepool_types.go:22:2: Expected 'i', Found '"' at exp/api/v1beta1/azuremachinepool_types.go[line 22,col 2] (gci)
	"sigs.k8s.io/cluster-api-provider-azure/api/v1beta1"
	^
exp/api/v1beta1/azuremachinepool_types.go:23:2: ST1019(related information): other import of "sigs.k8s.io/cluster-api-provider-azure/api/v1beta1" (stylecheck)
	infrav1 "sigs.k8s.io/cluster-api-provider-azure/api/v1beta1"
	^

[dthorsen]

This also needs a make generate-manifests run and committed. There are changes to the azuremachinepools CRD yaml that need to be generated.

diff --git a/config/crd/bases/infrastructure.cluster.x-k8s.io_azuremachinepools.yaml b/config/crd/bases/infrastructure.cluster.x-k8s.io_azuremachinepools.yaml
index a206f603..0b5229f1 100644
--- a/config/crd/bases/infrastructure.cluster.x-k8s.io_azuremachinepools.yaml
+++ b/config/crd/bases/infrastructure.cluster.x-k8s.io_azuremachinepools.yaml
@@ -1647,11 +1647,16 @@ spec:
                     description: Network Interfaces to attach to the to a virtual
                       machine
                     items:
+                      description: Network Interfaces to attach to each VM
                       properties:
                         acceleratedNetworking:
                           type: boolean
+                        id:
+                          type: string
                         ipConfigs:
                           items:
+                            description: IP Configuration defines options to confiure
+                              a network interface
                             properties:
                               privateIP:
                                 type: string

[dthorsen]