cluster-api-provider-metal3: Support for Failure Domains in CAPM3

User Story

As an operator who has placed their baremetal infrastructure across different failure domains (FDs), I would like CAPM3 to associate Nodes with BMHs from the desired failure domain.

Detailed Description

CAPI supports failure domains for both control-plane and worker nodes (see CAPI provider contract for Provider Machine as well Provider Cluster types). Here is the general flow:

1. CAPI will look for the set of FailureDomains in the ProviderCluster.Spec
2. The field is copied to the Cluster.Status.FailureDomains
3. During KCP or MD scale up events, a FD will be choosen from this set and it’s value placed in Machine.Spec.FailureDomain. Currently, CAPI tries to equally balance Machines across all FDs.
4. It is expected that providers will use this chosen FD in the Machine.Spec in deciding where to place the provider specific machine. In the case of metal3, we want CAPM3 to associate the Metal3Machine with the corresponding BMH in the desired FD.

BMH Selection using Labels.

1. The operator labels the BMH resource based on the physical location of the host. For example, the following standard label could be used on the BMH: infrastructure.cluster.x-k8s.io/failure-domain=<my-fd-1>
2. Today, CAPM3 chooseHost() func associates a Metal3Machine with a specific BMH based on labels specified in Metal3Machine.Spec.HostSelector.MatchLabels. We can expand this capability.
3. The HostSelector field is used to narrow down the set of available BMHs that meet the selection criteria. When FDs are being utilized, we can simply insert the above label into the HostSelector.MatchLabels.

Anything else you would like to add:

Related issues: https://github.com/kubernetes-sigs/cluster-api/issues/5666 https://github.com/kubernetes-sigs/cluster-api/issues/5667

/kind feature