Deploy MetalLB speakers on every workload cluster node by default

Summary

Currently in charts/sylva-units/values.yaml, the metallb.helmrelease_spec.values.speaker.nodeSelector restricts the speaker deployment to control plane nodes. MetalLB is also used to advertise workload service VIPs. Some use-cases require such avertissement on a secondary network which is only connected to machine-deployment (worker) nodes (the control plane node are only connected to the primary network). Then the current speaker deployment restriction prevents such possibility.

Details

By removing the metallb.helmrelease_spec.values.speaker.nodeSelector, the speakers would be deployed on every node making such use-case feasible.