Delete the out-of-tree PV labeler controller

[andrewsykim]

What type of PR is this?
/kind cleanup

What this PR does / why we need it:
Removes the PersistentVolume labeler controller. This is a controller that runs as part of the CCM (i.e. meant for out-of-tree providers). With Initializer support removed for v1.14, this controller is now effectively useless because it would only check for PVs with initializers enabled.

Some justifications for this change:

• we could not find any provider that relied on this controller (because they never created the InitializerConfiguration resource for PVs). For the few out-of-tree providers that have reported usage of this feature, we added corresponding volumes to the in-tree admission controller (vSphere Applies zone labels to newly created vsphere volumes #72687 & Cinder Add Cinder to PersistentVolumeLabel Admission Controller #73102)
• This controller also has some serious bugs and lacked feature parity with the in-tree PersistentVolumeLabel admission controller. The most notable is the fact that the out-of-tree PVL controller would apply failure domain labels to all PVs as long as the cloud provider implemented GetLabelsForVolume. This is a wrong assumption (at least in comparison to the in-tree admission controller) and could result in a segfault.
• Longer term, we want to only be using PV.NodeAffinity rather than labels for zone topology scheduling. SIG Cloud Provider & SIG Storage will be working on a longer-term out-of-tree solution for this in v1.15.

Which issue(s) this PR fixes:
Part of kubernetes/cloud-provider#4

Special notes for your reviewer:
More discussions around the intentions of this PR in kubernetes/cloud-provider#4

SIG cloud provider mailing list thread: https://groups.google.com/forum/#!topic/kubernetes-sig-cloud-provider/jZUB-Qk4S-M

Does this PR introduce a user-facing change?:

Remove the out-of-tree PersistentVolumeLabel controller because it cannot run without Initializers (removed in v1.14). If you are using AWS EBS, GCE PD, Azure Disk, Cinder Disk or vSphere volumes and rely on zone labels, then enable the `PersistentVolumeLabel` admission controller in the `kube-apiserver` in the `--enable-admission-plugins` flag. 

[andrewsykim]

/sig storage
/sig cloudprovider

[andrewsykim]

/area cloudprovider
/priorty important-soon

[andrewsykim]

/priority important-soon

[andrewsykim]

/assign @dims @msau42 @liggitt

[dims]

/approve
/lgtm

(cross my fingers about the CI jobs!)

[andrewsykim]

/milestone v1.14

[roycaihw]

/assign @cheftako

[liggitt]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: andrewsykim, dims, liggitt

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Needs approval from an approver in each of these files:

• cmd/cloud-controller-manager/OWNERS [andrewsykim,liggitt]
• pkg/controller/cloud/OWNERS [andrewsykim,liggitt]
• pkg/kubeapiserver/OWNERS [liggitt]

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