cmd: Create minimal cluster-version-operator-tests CLI

Create a minimal cluster-version-operator-tests CLI application, which has no tests.

The application will result in a tests extension binary that will extend
the openshift-tests binary with CVO tests that will reside in the CVO repository
using the openshift-tests-extension [1] framework.

Verifying that no tests are present:

```sh
$ ./_output/linux/amd64/openshift-tests-extension list
null
```

[1]: https://github.com/openshift-eng/openshift-tests-extension

Author: DavidHurta

cmd/cluster-version-operator-tests/main.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"os"
+
+	"github.com/spf13/cobra"
+
+	"github.com/openshift-eng/openshift-tests-extension/pkg/cmd"
+	"github.com/openshift-eng/openshift-tests-extension/pkg/extension"
+	"github.com/openshift-eng/openshift-tests-extension/pkg/extension/extensiontests"
+)
+
+func main() {
+	registry := extension.NewRegistry()
+	ext := extension.NewExtension("openshift", "payload", "cluster-version-operator")
+
+	var specs extensiontests.ExtensionTestSpecs
+	ext.AddSpecs(specs)
+	registry.Register(ext)
+
+	root := &cobra.Command{
+		Long: "OpenShift Tests Extension for Cluster Version Operator",
+	}
+	root.AddCommand(cmd.DefaultExtensionCommands(registry)...)
+
+	if err := func() error {
+		return root.Execute()
+	}(); err != nil {
+		os.Exit(1)
+	}
+}