feat: Add POLARS_ALLOW_UNSECURED_TEMP_DIR environment variable

[nameexhaustion]

In the event something goes wrong with the newly added permission setting behavior from #21125, this provides a way to allow for any errors to be ignored so that users can avoid needing to downgrade their polars version.

[codecov]

Codecov Report

Attention: Patch coverage is 71.42857% with 2 lines in your changes missing coverage. Please review.

Project coverage is 79.87%. Comparing base (5121c53) to head (d092d1d).
Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-io/src/path_utils/mod.rs	71.42%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #21137   +/-   ##
=======================================
  Coverage   79.86%   79.87%           
=======================================
  Files        1593     1593           
  Lines      227453   227457    +4     
  Branches     2600     2600           
=======================================
+ Hits       181662   181676   +14     
+ Misses      45194    45184   -10     
  Partials      597      597           

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