[SPARK-49718][PS] Switch Scatter plot to sampled data

### What changes were proposed in this pull request?
Switch `Scatter` plot to sampled data

### Why are the changes needed?
when the data distribution has relationship with the order, the first n rows will not be representative of the whole dataset

for example:
```
import pandas as pd
import numpy as np
import pyspark.pandas as ps

# ps.set_option("plotting.max_rows", 10000)
np.random.seed(123)

pdf = pd.DataFrame(np.random.randn(10000, 4), columns=list('ABCD')).sort_values("A")
psdf = ps.DataFrame(pdf)

psdf.plot.scatter(x='B', y='A')
```

all 10k datapoints:
![image](https://github.com/user-attachments/assets/72cf7e97-ad10-41e0-a8a6-351747d5285f)

before (first 1k datapoints):
![image](https://github.com/user-attachments/assets/1ed50d2c-7772-4579-a84c-6062542d9367)

after (sampled 1k datapoints):
![image](https://github.com/user-attachments/assets/6c684cba-4119-4c38-8228-2bedcdeb9e59)

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

### How was this patch tested?
ci and manually test

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

Closes apache#48164 from zhengruifeng/ps_scatter_sampling.

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

python/pyspark/pandas/plot/core.py

@@ -479,7 +479,7 @@ class PandasOnSparkPlotAccessor(PandasObject):
         "pie": TopNPlotBase().get_top_n,
         "bar": TopNPlotBase().get_top_n,
         "barh": TopNPlotBase().get_top_n,
-        "scatter": TopNPlotBase().get_top_n,
+        "scatter": SampledPlotBase().get_sampled,
         "area": SampledPlotBase().get_sampled,
         "line": SampledPlotBase().get_sampled,
     }