fs: cache context lookup in vectored io loops

[mertcanaltin]

I tried to prevent the call from being repeated

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.54%. Comparing base (903f647) to head (fe4be58).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_file.cc	50.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #61387   +/-   ##
=======================================
  Coverage   88.54%   88.54%           
=======================================
  Files         704      704           
  Lines      208793   208795    +2     
  Branches    40307    40303    -4     
=======================================
+ Hits       184866   184869    +3     
+ Misses      15913    15909    -4     
- Partials     8014     8017    +3     

Files with missing lines	Coverage Δ
src/node_file.cc	75.44% <50.00%> (-0.02%)	⬇️

... and 24 files with indirect coverage changes

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