Merge pull request #53136 from prydie/cloudprovider-import-comment

Automatic merge from submit-queue (batch tested with PRs 52630, 53110, 53136, 53075). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Note that all importing cloud-providers not required implementing out-of-tree cloud-provider

**What this PR does / why we need it**:

[The documentation indicates](https://github.com/kubernetes/kubernetes.github.io/pull/5400/files#diff-9585dc0efb0450fd68728e7511754717R29) that authors of of out-of-tree cloud providers should

> Use [main.go in cloud-controller-manager](https://github.com/kubernetes/kubernetes/blob/master/cmd/cloud-controller-manager/controller-manager.go) from Kubernestes core as a template for your main.go

This PR adds a comment to indicate that when doing so they do not need to import all in-tree cloud-providers. This mistake had been made in the OCI, DO, and Rancher CCMs.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```

/cc @luxas @wlan0 @andrewsykim @jhorwit2
/area cloudprovider
/sig cluster-lifecycle

cmd/cloud-controller-manager/controller-manager.go

@@ -29,6 +29,8 @@ import (
 	"k8s.io/kubernetes/cmd/cloud-controller-manager/app/options"
 	_ "k8s.io/kubernetes/pkg/client/metrics/prometheus" // for client metric registration
 	"k8s.io/kubernetes/pkg/cloudprovider"
+	// NOTE: Importing all in-tree cloud-providers is not required when
+	// implementing an out-of-tree cloud-provider.
 	_ "k8s.io/kubernetes/pkg/cloudprovider/providers"
 	_ "k8s.io/kubernetes/pkg/version/prometheus" // for version metric registration
 	"k8s.io/kubernetes/pkg/version/verflag"