fix: Ignore file cache allocation error if fallocate() is not permitted

[nameexhaustion]

Update to automatically ignore the error without needing the environment variable to be set if the system does not permit fallocate().

ref #17946

[codecov]

Codecov Report

Attention: Patch coverage is 31.25000% with 11 lines in your changes missing coverage. Please review.

Project coverage is 79.77%. Comparing base (3696e53) to head (26b5d1a).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-io/src/file_cache/entry.rs	31.25%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #20796      +/-   ##
==========================================
- Coverage   79.78%   79.77%   -0.01%     
==========================================
  Files        1561     1561              
  Lines      222015   222019       +4     
  Branches     2533     2533              
==========================================
- Hits       177135   177125      -10     
- Misses      44296    44310      +14     
  Partials      584      584              

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