[SPARK-24973][PYTHON] Add numIter to Python ClusteringSummary

## What changes were proposed in this pull request?

Add numIter to Python version of ClusteringSummary

## How was this patch tested?

Modified existing UT test_multiclass_logistic_regression_summary

Author: Huaxin Gao <huaxing@us.ibm.com>

Closes #21925 from huaxingao/spark-24973.

python/pyspark/ml/clustering.py

@@ -88,6 +88,14 @@ def clusterSizes(self):
         """
         return self._call_java("clusterSizes")
 
+    @property
+    @since("2.4.0")
+    def numIter(self):
+        """
+        Number of iterations.
+        """
+        return self._call_java("numIter")
+
 
 class GaussianMixtureModel(JavaModel, JavaMLWritable, JavaMLReadable):
     """

python/pyspark/ml/tests.py

@@ -1888,6 +1888,7 @@ def test_gaussian_mixture_summary(self):
         self.assertTrue(isinstance(s.cluster, DataFrame))
         self.assertEqual(len(s.clusterSizes), 2)
         self.assertEqual(s.k, 2)
+        self.assertEqual(s.numIter, 3)
 
     def test_bisecting_kmeans_summary(self):
         data = [(Vectors.dense(1.0),), (Vectors.dense(5.0),), (Vectors.dense(10.0),),
@@ -1903,6 +1904,7 @@ def test_bisecting_kmeans_summary(self):
         self.assertTrue(isinstance(s.cluster, DataFrame))
         self.assertEqual(len(s.clusterSizes), 2)
         self.assertEqual(s.k, 2)
+        self.assertEqual(s.numIter, 20)
 
     def test_kmeans_summary(self):
         data = [(Vectors.dense([0.0, 0.0]),), (Vectors.dense([1.0, 1.0]),),
@@ -1918,6 +1920,7 @@ def test_kmeans_summary(self):
         self.assertTrue(isinstance(s.cluster, DataFrame))
         self.assertEqual(len(s.clusterSizes), 2)
         self.assertEqual(s.k, 2)
+        self.assertEqual(s.numIter, 1)
 
 
 class KMeansTests(SparkSessionTestCase):