Use try-with-resources to close file walk stream in LocalPinotFS

[yashmayya]

From the File::walk Javadoc:

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.17%. Comparing base (59551e4) to head (7b8f8ac).
Report is 382 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #13029      +/-   ##
============================================
+ Coverage     61.75%   62.17%   +0.42%     
+ Complexity      207      198       -9     
============================================
  Files          2436     2502      +66     
  Lines        133233   136671    +3438     
  Branches      20636    21164     +528     
============================================
+ Hits          82274    84978    +2704     
- Misses        44911    45407     +496     
- Partials       6048     6286     +238     

Flag	Coverage Δ
custom-integration1	<0.01% <0.00%> (-0.01%)	⬇️
integration	<0.01% <0.00%> (-0.01%)	⬇️
integration1	<0.01% <0.00%> (-0.01%)	⬇️
integration2	0.00% <0.00%> (ø)
java-11	62.14% <100.00%> (+0.43%)	⬆️
java-21	62.06% <100.00%> (+0.43%)	⬆️
skip-bytebuffers-false	62.16% <100.00%> (+0.41%)	⬆️
skip-bytebuffers-true	62.04% <100.00%> (+34.31%)	⬆️
temurin	62.17% <100.00%> (+0.42%)	⬆️
unittests	62.17% <100.00%> (+0.42%)	⬆️
unittests1	46.74% <100.00%> (-0.16%)	⬇️
unittests2	27.94% <0.00%> (+0.20%)	⬆️

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