User Story:

As a service provider, when I create a HostedCluster in a management cluster with mixed arch nodes, a particular HostedCluster that only fits one arch, should only be scheduled on nodes that match that arch.

For example, if my release playload is amd64 only, then the HyperShift operator can automatically add the 
`kubernets.io/arch=amd64` selector to the control plane pods of the HostedCluster.