feat: Expand NDJson glob into one SCAN

[coastalwhite]

This properly expands globs in NDJson into one scan with multiple files.

This also fixes the n_rows parameter for DataFrame::scan_ndjson with multiple files.

[codecov]

Codecov Report

Attention: Patch coverage is 92.98246% with 4 lines in your changes missing coverage. Please review.

Project coverage is 80.85%. Comparing base (4d15fd4) to head (1419041).

Files	Patch %	Lines
...tes/polars-mem-engine/src/executors/scan/ndjson.rs	86.36%	3 Missing ⚠️
crates/polars-lazy/src/scan/ndjson.rs	97.14%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17063      +/-   ##
==========================================
- Coverage   80.89%   80.85%   -0.04%     
==========================================
  Files        1455     1455              
  Lines      190961   191011      +50     
  Branches     2723     2723              
==========================================
- Hits       154473   154450      -23     
- Misses      35984    36057      +73     
  Partials      504      504              

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