[SPARK-49530][PYTHON][CONNECT] Support kde/density plots

[xinrong-meng]

What changes were proposed in this pull request?

Support kde/density plots with plotly backend on both Spark Connect and Spark classic.

Why are the changes needed?

While Pandas on Spark supports plotting, PySpark currently lacks this feature. The proposed API will enable users to generate visualizations. This will provide users with an intuitive, interactive way to explore and understand large datasets directly from PySpark DataFrames, streamlining the data analysis workflow in distributed environments.

See more at PySpark Plotting API Specification in progress.

Part of https://issues.apache.org/jira/browse/SPARK-49530.

Does this PR introduce any user-facing change?

Yes. kde/density plots are supported as shown below.

>>> data = [
...     (1.0, 4.0),
...     (2.0, 4.0),
...     (2.5, 4.5),
...     (3.0, 5.0),
...     (3.5, 5.5),
...     (4.0, 6.0),
...     (5.0, 6.0)
... ]
>>> columns = ["x", "y"]
>>> df = spark.createDataFrame(data, columns)
>>> fig1 = df.plot.kde(column=["x", "y"], bw_method=0.3, ind=100)
>>> fig1.show()  # see below
>>> fig2 = df.plot(kind="kde", column="x", bw_method=0.3, ind=20)
>>> fig2.show()  # see below

fig1:

fig2:

How was this patch tested?

Unit tests.

Was this patch authored or co-authored using generative AI tooling?

No.

[xinrong-meng]

Create https://issues.apache.org/jira/browse/SPARK-49999 for a follow-up on optional "column" parameter support in box, kde and hist plots

[xinrong-meng]

Create https://issues.apache.org/jira/browse/SPARK-50000 for optional "bw_method" in both Pandas on Spark and PySpark

[xinrong-meng]

@zhengruifeng @HyukjinKwon may I get a review please?