src: cleanup uv_fs_req before uv_fs_stat on existSync

[RafaelGSS]

src: cleanup uv_fs_req before uv_fs_stat on existSync

Calling uv_fs_stat() without first calling
uv_fs_req_cleanup() overwrites the pointer to the
previously allocated buffer leading to a memory
leak on windows

cc: @bnoordhuis

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/67765/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.09%. Comparing base (a7a37c3) to head (1ec0548).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #58915      +/-   ##
==========================================
- Coverage   90.11%   90.09%   -0.02%     
==========================================
  Files         640      640              
  Lines      188427   188427              
  Branches    36956    36968      +12     
==========================================
- Hits       169792   169756      -36     
- Misses      11348    11385      +37     
+ Partials     7287     7286       -1     

Files with missing lines	Coverage Δ
src/node_file.cc	75.86% <ø> (+0.07%)	⬆️

... and 26 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/67768/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/67773/