Current state:

cluster-api-provider has no logic for handling affinity groups

What we want:

Cluster API provider should expose logic for adding a created machine to existing affinity groups by adding a field for affinity groups in the machine spec.

This means that when you create a machine set you can decide that all the machines will join an *existing affinity group* in the cluster.

What is not supported:

1. Adding the machine to an affinity group that is not in the cluster, meaning that if the affinity group doesn't exist when the machine is created then it will not be added to the group.
2. Updating the field of the machine is not supported, if you update the field on an existing machine nothing will happen.
3. Creating/Deleting Affinity groups from the cluster

How to test?

Positive flow:
1. create an 2 affinity groups on the RHV cluster (can be done via UI), for example "test-affinity-group-1" and "test-affinity-group-2"
2. create a machine set with the affinity group, for example:
```yaml
apiVersion: machine.openshift.io/v1beta1
kind: MachineSet
metadata:
  labels:
    machine.openshift.io/cluster-api-cluster: ovirt11-CLUSTERNAME
    machine.openshift.io/cluster-api-machine-role: worker
    machine.openshift.io/cluster-api-machine-type: worker
spec:
  replicas: 1
  selector:
    matchLabels:
      machine.openshift.io/cluster-api-cluster: ovirt11-CLUSTERNAME
      machine.openshift.io/cluster-api-machineset: ovirt11-CLUSTERNAME-worker-1
  template:
    metadata:
      labels:
        machine.openshift.io/cluster-api-cluster: ovirt11-CLUSTERNAME
        machine.openshift.io/cluster-api-machine-role: worker
        machine.openshift.io/cluster-api-machine-type: worker
        machine.openshift.io/cluster-api-machineset: ovirt11-CLUSTERNAME-worker-1
    spec:
      providerSpec:
        value:
          affinity_groups_names:
          - test-affinity-group-1
          - test-affinity-group-2
          apiVersion: ovirtproviderconfig.machine.openshift.io/v1beta1
          cluster_id: CLUSTERID
          cpu:
            cores: 8
            sockets: 1
            threads: 1
          credentialsSecret:
            name: ovirt-credentials
          kind: OvirtMachineProviderSpec
          memory_mb: 16000
          os_disk:
            size_gb: 31
          template_name: ovirt11-CLUSTERNAME-rhcos
          type: server
          userDataSecret:
            name: worker-user-data
```
3. Verify that 1 machine is created and added to the affinity groups.
4. scale to 2 replicas and make sure that another machine is created and added to the affinity groups
5. scale down and make sure the machine is deleted and removed from the affinity groups

Negative flow suggestions:
- try an affinity group that doesn't exist in the RHV cluster -> the Machine should fail to create, machine is in down state on RHV and logs show errors.
- try an affinity group that exist on a different RHV cluster -> the Machine should fail to create, machine is in down state on RHV and logs show errors.