refactor(python): Split file of lazyframe methods

[eitsupi]

As with DataFrame, it would be better to split the io-related functions into separate files for LazyFrame as well.

[codecov]

Codecov Report

Attention: Patch coverage is 99.34354% with 3 lines in your changes missing coverage. Please review.

Project coverage is 79.48%. Comparing base (414d883) to head (0bca62c).
Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-python/src/lazyframe/io.rs	99.34%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #19937       +/-   ##
===========================================
+ Coverage   59.28%   79.48%   +20.19%     
===========================================
  Files        1555     1556        +1     
  Lines      216180   216181        +1     
  Branches     2456     2456               
===========================================
+ Hits       128155   171824    +43669     
+ Misses      87467    43799    -43668     
  Partials      558      558               

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