e2e: Add catalog source health check to assertSubscription

By OLM design, a subscription cannot be installed unless all catalog
sources are healthy, regardless of which catalog source the subscription
uses. This commit updates the `assertSubscription` helper to verify
catalog source health as part of its checks.

Author: alebedev87

test/e2e/util_gatewayapi_test.go

@@ -574,6 +574,16 @@ func assertSubscription(t *testing.T, namespace, subName string) error {
 			return false, nil
 		}
 		t.Logf("found subscription %s at installed version %s", subscription.Name, subscription.Status.InstalledCSV)
+		for _, c := range subscription.Status.Conditions {
+			if c.Type == operatorsv1alpha1.SubscriptionCatalogSourcesUnhealthy {
+				if c.Status == corev1.ConditionTrue {
+					t.Logf("catalog sources unhealthy for subscription %s, retrying...", subName)
+					return false, nil
+				}
+				break
+			}
+		}
+		t.Logf("all catalog sources healthy for subscription %s", subscription.Name)
 		return true, nil
 	})
 	return err