refactor(rust): Improve dot formatting of new-streaming parquet source

[nameexhaustion]

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 79.83%. Comparing base (69a2bef) to head (4dd3f05).
Report is 73 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-stream/src/physical_plan/mod.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18367      +/-   ##
==========================================
- Coverage   79.84%   79.83%   -0.02%     
==========================================
  Files        1496     1496              
  Lines      200333   200335       +2     
  Branches     2841     2841              
==========================================
- Hits       159957   159931      -26     
- Misses      39851    39879      +28     
  Partials      525      525              

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