feat: Closeable files on unix

[ritchie46]

#21002

[codecov]

Codecov Report

Attention: Patch coverage is 91.30435% with 8 lines in your changes missing coverage. Please review.

Project coverage is 79.91%. Comparing base (a1c6834) to head (5575ed3).
Report is 41 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-utils/src/file.rs	89.47%	4 Missing ⚠️
crates/polars-python/src/conversion/mod.rs	0.00%	2 Missing ⚠️
crates/polars-python/src/file.rs	90.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #21588      +/-   ##
==========================================
+ Coverage   79.80%   79.91%   +0.11%     
==========================================
  Files        1604     1605       +1     
  Lines      231362   231582     +220     
  Branches     2639     2639              
==========================================
+ Hits       184629   185065     +436     
+ Misses      46124    45908     -216     
  Partials      609      609              

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[github-actions]

The uncompressed lib size after this PR is 41.9499 MB.

[github-actions]

The uncompressed lib size after this PR is 41.9512 MB.