fix(gin): close os.File in RunFd to prevent resource leak

[1911860538]

os.NewFile creates a *os.File object that holds a reference to
the file descriptor. Even though the file descriptor itself is
not opened by os.NewFile, the *os.File object needs to be cleaned
up to release its reference.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.96%. Comparing base (3dc1cd6) to head (f600b0a).
⚠️ Report is 202 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4422      +/-   ##
==========================================
- Coverage   99.21%   98.96%   -0.25%     
==========================================
  Files          42       44       +2     
  Lines        3182     2900     -282     
==========================================
- Hits         3157     2870     -287     
- Misses         17       19       +2     
- Partials        8       11       +3     

Flag	Coverage Δ
	?
--ldflags="-checklinkname=0" -tags sonic	98.95% <100.00%> (?)
-tags go_json	98.88% <100.00%> (?)
-tags nomsgpack	98.94% <100.00%> (?)
go-1.18	?
go-1.19	?
go-1.20	?
go-1.21	?
go-1.24	98.96% <100.00%> (?)
go-1.25	98.96% <100.00%> (?)
macos-latest	98.96% <100.00%> (-0.25%)	⬇️
ubuntu-latest	98.96% <100.00%> (-0.25%)	⬇️

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[1911860538]

Verified safe since net.FileListener internally duplicates the
file descriptor via dup(), creating a separate socket handle.
Closing the original *os.File only releases its own reference and
does not close the underlying network socket used by the listener.

Therefore, defer f.Close() does not interfere with existing connections
or cause "use of closed network connection" errors, including in
graceful restart scenarios where the listener is inherited across processes.