Make Cloud Provider Equinix Metal optional

[displague]

In some environments, users may wish to use an independent Cloud Provider controller (aka CCM) that can treat all Equinix Metal devices and devices from other cloud providers as pure baremetal behind a Layer2 network.

In these environments, the 'Cloud Provider: Equinix Metal' (CPEM) controller should not set the Node providerID nor manage labels and annotations on Nodes. Another CCM may take on those responsibilities in a baremetal + L2 (cloud-agnostic) way.

When CPEM is removed, users still wanting to take advantage of LoadBalancer services may continue to do so using MetalLB or Kube-VIP. A benefit of CPEM is that it will provision or discover available IP reservations from Equinix Metal APIs and populate the Service address accordingly.

Users choosing to omit CPEM from their Anthos installation will want to find an alternative approach to dynamic provisioning of IP Addresses, or use static addressing.

[displague]

We may not pursue this if kubernetes-sigs/cloud-provider-equinix-metal#156 (CPEM without the Node Controller) fulfills the need.

[c0dyhi11]

I think this is no longer an issue. Since we can now use the CCM properly and provide the "ProviderID"

@displague should we close?