feat: change to get macaddress from annotation (backport #74)

[mergify]

IMPORTANT: Please do not create a Pull Request without creating an issue first.

Problem:
The Harvester controller changed to save macaddress on annotation and patch to spec when the VM is down. The vm-dhcp-controller watches VM spec to allocate IP, so it cannot work after v1.6.

harvester/harvester#8339

Solution:
Change to get macaddress from annotation.

Related Issue:
harvester/harvester#9212

Test plan:

1. Create a Harvester cluster.
2. Add dhcp addon.

apiVersion: harvesterhci.io/v1beta1
kind: Addon
metadata:
  labels:
    addon.harvesterhci.io/experimental: 'true'
  name: harvester-vm-dhcp-controller
  namespace: harvester-system
spec:
  chart: harvester-vm-dhcp-controller
  enabled: true
  repo: https://charts.harvesterhci.io
  valuesContent: |
    image:
      repository: frankyang/harvester-vm-dhcp-controller
      pullPolicy: IfNotPresent
      tag: HARV-9212-head
    agent:
      repository: frankyang/harvester-vm-dhcp-agent
      pullPolicy: IfNotPresent
      tag: HARV-9212-head
    webhook:
      repository: frankyang/harvester-vm-dhcp-webhook
      pullPolicy: IfNotPresent
      tag: HARV-9212-head
  version: 1.6.0

3. Create a VM network vlan1.
4. Create an ip pool.

cat <<EOF | kubectl apply -f -
apiVersion: network.harvesterhci.io/v1alpha1
kind: IPPool
metadata:
  name: vlan1
  namespace: default
spec:
  ipv4Config:
    serverIP: 192.168.48.77
    cidr: 192.168.48.0/24
    pool:
      start: 192.168.48.81
      end: 192.168.48.90
      exclude:
      - 192.168.48.81
      - 192.168.48.90
    router: 192.168.48.1
    dns:
    - 1.1.1.1
    leaseTime: 300
  networkName: default/vlan1
EOF

5. Create a VM with this ip pool.
6. Check the VM gets this IP.

> ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 52:99:36:c8:85:22 brd ff:ff:ff:ff:ff:ff
    inet 192.168.48.82/24 brd 192.168.48.255 scope global dynamic enp1s0
       valid_lft 248sec preferred_lft 248sec
    inet6 fe80::5099:36ff:fec8:8522/64 scope link 
       valid_lft forever preferred_lft forever
```<hr>This is an automatic backport of pull request #74 done by [Mergify](https://mergify.com).