pkg/internal: Add log level constants

These constants can be simply used when logging across the project instead
of specifying the level by a number. The descriptions and the values will
also guide developers when deciding what log level to choose.

For example:

```go
  import "github.com/openshift/cluster-version-operator/pkg/internal"

  klog.V(internal.Debug).Infof("")
```

The descriptions of the values are extracted from the used API type [1].

[1]: https://github.com/openshift/api/blob/744790f2cff777b1bb29bdccce10e4e84cff0a69/operator/v1/types.go#L94-L109

Author: DavidHurta

pkg/internal/constants.go

@@ -1,5 +1,7 @@
 package internal
 
+import "k8s.io/klog/v2"
+
 const (
 	ConfigNamespace        = "openshift-config"
 	ConfigManagedNamespace = "openshift-config-managed"
@@ -8,3 +10,22 @@ const (
 	InstallerConfigMap     = "openshift-install"
 	ManifestsConfigMap     = "openshift-install-manifests"
 )
+
+var (
+	// Normal is the default. Normal, working log information, everything is fine, but helpful notices for auditing or
+	// common operations. In kube, this is probably glog=2.
+	Normal klog.Level = 2
+
+	// Debug is used when something went wrong. Even common operations may be logged, and less helpful but more
+	// quantity of notices. In kube, this is probably glog=4.
+	Debug klog.Level = 4
+
+	// Trace is used when something went really badly and even more verbose logs are needed. Logging every function
+	// call as part of a common operation, to tracing execution of a query. In kube, this is probably glog=6.
+	Trace klog.Level = 6
+
+	// TraceAll is used when something is broken at the level of API content/decoding. It will dump complete body
+	// content. If you turn this on in a production cluster prepare from serious performance issues and massive
+	// amounts of logs. In kube, this is probably glog=8.
+	TraceAll klog.Level = 8
+)