Add params to the data splitter for visibility

[bchen1116]

With this change, when we call automl.data_splitter, we will see

BalancedClassificationDataCVSplit(balanced_ratio=4, min_percentage=0.1,
                 min_samples=100, n_splits=3, random_seed=0, shuffle=True)

rather than

BalancedClassificationDataCVSplit(balanced_ratio=None, min_percentage=None,
                 min_samples=None, n_splits=3, random_seed=0, shuffle=True)

[codecov]

Codecov Report

Merging #1966 (6a1c537) into main (064b821) will increase coverage by 0.1%.
The diff coverage is 100.0%.

@@            Coverage Diff            @@
##             main    #1966     +/-   ##
=========================================
+ Coverage   100.0%   100.0%   +0.1%     
=========================================
  Files         273      273             
  Lines       22391    22406     +15     
=========================================
+ Hits        22385    22400     +15     
  Misses          6        6             

Impacted Files	Coverage Δ
evalml/tests/automl_tests/test_automl.py	100.0% <ø> (ø)
...data_splitters/balanced_classification_splitter.py	100.0% <100.0%> (ø)
...ests/test_balanced_classification_data_splitter.py	100.0% <100.0%> (ø)

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[angela97lin]

If I'm understanding correctly, the test in evalml/tests/automl_tests/test_automl.py tests this updated change, and then the test you added in evalml/tests/preprocessing_tests/test_balanced_classification_data_splitter.py is just to check for defaults / set attributes? LGTM!