[SPARK-48184][PYTHON][CONNECT] Always set the seed of `Dataframe.samp…

…le` in Client side

### What changes were proposed in this pull request?
Always set the seed of `Dataframe.sample` in Client side

### Why are the changes needed?
Bug fix

If the seed is not set in Client, it will be set in server side with a random int

https://github.com/apache/spark/blob/c4df12cc884cddefcfcf8324b4d7b9349fb4f6a0/connector/connect/server/src/main/scala/org/apache/spark/sql/connect/planner/SparkConnectPlanner.scala#L386

which cause inconsistent results in multiple executions

In Spark Classic:
```
In [1]: df = spark.range(10000).sample(0.1)

In [2]: [df.count() for i in range(10)]
Out[2]: [1006, 1006, 1006, 1006, 1006, 1006, 1006, 1006, 1006, 1006]
```

In Spark Connect:

before:
```
In [1]: df = spark.range(10000).sample(0.1)

In [2]: [df.count() for i in range(10)]
Out[2]: [969, 1005, 958, 996, 987, 1026, 991, 1020, 1012, 979]
```

after:
```
In [1]: df = spark.range(10000).sample(0.1)

In [2]: [df.count() for i in range(10)]
Out[2]: [1032, 1032, 1032, 1032, 1032, 1032, 1032, 1032, 1032, 1032]
```

### Does this PR introduce _any_ user-facing change?
yes, bug fix

### How was this patch tested?
ci

### Was this patch authored or co-authored using generative AI tooling?
no

Closes apache#46456 from zhengruifeng/py_connect_sample_seed.

Authored-by: Ruifeng Zheng <ruifengz@apache.org>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>

python/pyspark/sql/connect/dataframe.py

@@ -813,7 +813,7 @@ def sample(
         if withReplacement is None:
             withReplacement = False
 
-        seed = int(seed) if seed is not None else None
+        seed = int(seed) if seed is not None else random.randint(0, sys.maxsize)
 
         return DataFrame(
             plan.Sample(

python/pyspark/sql/tests/connect/test_connect_plan.py

@@ -443,7 +443,7 @@ def test_sample(self):
         self.assertEqual(plan.root.sample.lower_bound, 0.0)
         self.assertEqual(plan.root.sample.upper_bound, 0.3)
         self.assertEqual(plan.root.sample.with_replacement, False)
-        self.assertEqual(plan.root.sample.HasField("seed"), False)
+        self.assertEqual(plan.root.sample.HasField("seed"), True)
         self.assertEqual(plan.root.sample.deterministic_order, False)
 
         plan = (

python/pyspark/sql/tests/test_dataframe.py

@@ -430,6 +430,11 @@ def test_sample(self):
             IllegalArgumentException, lambda: self.spark.range(1).sample(-1.0).count()
         )
 
+    def test_sample_with_random_seed(self):
+        df = self.spark.range(10000).sample(0.1)
+        cnts = [df.count() for i in range(10)]
+        self.assertEqual(1, len(set(cnts)))
+
     def test_toDF_with_string(self):
         df = self.spark.createDataFrame([("John", 30), ("Alice", 25), ("Bob", 28)])
         data = [("John", 30), ("Alice", 25), ("Bob", 28)]