Add HRA printer column "SCHEDULE" (#561)

Adds a column to help the operator see if they configured HRA.Spec.ScheduledOverrides correctly, in a form of "next override schedule recognized by the controller":

```
$ k get horizontalrunnerautoscaler
NAME                            MIN   MAX   DESIRED   SCHEDULE
actions-runner-aos-autoscaler   0     5     0
org                             0     5     0         min=0 time=2021-05-21 15:00:00 +0000 UTC
```

Ref https://github.com/actions-runner-controller/actions-runner-controller/issues/484

api/v1alpha1/zz_generated.deepcopy.go

@@ -250,6 +250,11 @@ func (in *HorizontalRunnerAutoscalerStatus) DeepCopyInto(out *HorizontalRunnerAu
 			(*in)[i].DeepCopyInto(&(*out)[i])
 		}
 	}
+	if in.ScheduledOverridesSummary != nil {
+		in, out := &in.ScheduledOverridesSummary, &out.ScheduledOverridesSummary
+		*out = new(string)
+		**out = **in
+	}
 }
 
 // DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new HorizontalRunnerAutoscalerStatus.