fs,win: do not add a second trailing slash in readdir

[Flarna]

Do not add a trailing slash if it was not removed by resolve in ToNamespacedPath.

Unfortunatelly I do not know how to test this without 3rd party tools descirbed in #58223.

Refs: #56110
Fixes: #58223

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.27%. Comparing base (861d624) to head (f8fd082).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #59847      +/-   ##
==========================================
+ Coverage   88.26%   88.27%   +0.01%     
==========================================
  Files         701      701              
  Lines      206774   206774              
  Branches    39778    39779       +1     
==========================================
+ Hits       182514   182540      +26     
+ Misses      16298    16236      -62     
- Partials     7962     7998      +36     

Files with missing lines	Coverage Δ
src/node_file.cc	75.63% <ø> (ø)

... and 44 files with indirect coverage changes

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