[SPARK-30378][ML][PySpark] Add getter/setter in Python FM

[huaxingao]

What changes were proposed in this pull request?

add getter/setter in Python FM

Why are the changes needed?

to be consistent with other algorithms

Does this PR introduce any user-facing change?

Yes.
add getter/setter in Python FMRegressor/FMRegressionModel/FMClassifier/FMClassificationModel

How was this patch tested?

doctest

[SparkQA]

Test build #115924 has finished for PR 27044 at commit c141f52.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
• class FMClassifier(JavaProbabilisticClassifier, _FactorizationMachinesParams, JavaMLWritable,
• class FMClassificationModel(JavaProbabilisticClassificationModel, _FactorizationMachinesParams,
• class _FactorizationMachinesParams(_JavaPredictorParams, HasMaxIter, HasStepSize, HasTol,
• class FMRegressor(JavaPredictor, _FactorizationMachinesParams, JavaMLWritable, JavaMLReadable):
• class FMRegressionModel(JavaPredictionModel, _FactorizationMachinesParams, JavaMLWritable,

[zhengruifeng]

Merged to master, thanks @huaxingao

[huaxingao]

Thank you very much!