refactor: move source assign package under split

[HuangZhenQiu]

Describe the issue this Pull Request addresses

move source assign package under split

Summary and Changelog

1. move source assign package under split for better modularization

Impact

none

Risk Level

none

Documentation Update

none

Contributor's checklist

• Read through contributor's guide
• Enough context is provided in the sections above
• Adequate tests were added if applicable

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.30%. Comparing base (fb7b1a5) to head (9d15e11).

Additional details and impacted files

@@            Coverage Diff            @@
##             master   #18253   +/-   ##
=========================================
  Coverage     57.30%   57.30%           
+ Complexity    18561    18550   -11     
=========================================
  Files          1945     1945           
  Lines        106256   106256           
  Branches      13131    13133    +2     
=========================================
+ Hits          60885    60887    +2     
+ Misses        39648    39643    -5     
- Partials       5723     5726    +3     

Flag	Coverage Δ
hadoop-mr-java-client	45.39% <ø> (-0.01%)	⬇️
spark-java-tests	47.43% <ø> (+<0.01%)	⬆️
spark-scala-tests	45.51% <ø> (+<0.01%)	⬆️

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see 4 files with indirect coverage changes

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[hudi-bot]

CI report:

• 9d15e11 Azure: SUCCESS

Bot commands

@hudi-bot supports the following commands:

• @hudi-bot run azure re-run the last Azure build