Set runtime logger for gardenlet

This was forgotten in gardener#5057 and prevents logs for packages used in gardenlet which were already migrated from `logrus` to `logr`.

cmd/gardenlet/app/gardenlet.go

@@ -70,6 +70,7 @@ import (
 	"k8s.io/client-go/tools/record"
 	"k8s.io/component-base/version"
 	"k8s.io/component-base/version/verflag"
+	runtimelog "sigs.k8s.io/controller-runtime/pkg/log"
 )
 
 // Options has all the context and parameters needed to run a Gardenlet.
@@ -244,6 +245,9 @@ func NewGardenlet(ctx context.Context, cfg *config.GardenletConfiguration) (*Gar
 		return nil, fmt.Errorf("error instantiating zap logger: %w", err)
 	}
 
+	// set the logger used by sigs.k8s.io/controller-runtime
+	runtimelog.SetLogger(log)
+
 	log.Info("Starting gardenlet", "version", version.Get())
 	log.Info("Feature Gates", "featureGates", gardenletfeatures.FeatureGate.String())