[MSINTEROP-1243] Add mirror for registry.stage.redhat.io to ICSP for operator install (#360)

Add mirror for registry.stage.redhat.io to icsp for operator install

Author: calebevans

ocp_utilities/operators.py

@@ -371,6 +371,10 @@ def _icsp(_repository_digest_mirrors: List[Dict[str, Any]]) -> None:
             "source": f"registry.redhat.io/{brew_image_repo}",
             "mirrors": [f"{brew_registry}/{brew_image_repo}"],
         },
+        {
+            "source": f"registry.stage.redhat.io/{brew_image_repo}",
+            "mirrors": [f"{brew_registry}/{brew_image_repo}"],
+        },
     ]
 
     if validating_webhook_configuration.exists: