[PR #10113/01302134 backport][3.11] Restore 304 performance after fixing FileResponse replace race

[patchback]

This is a backport of PR #10113 as merged into master (0130213).

Followup to #10101 to address the feedback in #10112

We can avoid opening the file is we are going to send a 304.

fixes #10112

[codspeed-hq]

CodSpeed Performance Report

Merging #10117 will improve performances by 17.37%

_{Comparing patchback/backports/3.11/0130213423d8d055ece27c36a4dcc96e524cbc1c/pr-10113 (d4b4b19) with 3.11 (78473b9)}

Summary

⚡ 1 improvements
✅ 46 untouched benchmarks

Benchmarks breakdown

	Benchmark	3.11	patchback/backports/3.11/0130213423d8d055ece27c36a4dcc96e524cbc1c/pr-10113	Change
⚡	test_simple_web_file_response_not_modified[pyloop]	67.7 ms	57.7 ms	+17.37%

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.06%. Comparing base (78473b9) to head (d4b4b19).
Report is 51 commits behind head on 3.11.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             3.11   #10117   +/-   ##
=======================================
  Coverage   98.06%   98.06%           
=======================================
  Files         123      123           
  Lines       37138    37147    +9     
  Branches     4468     4467    -1     
=======================================
+ Hits        36420    36429    +9     
  Misses        540      540           
  Partials      178      178           

Flag	Coverage Δ
CI-GHA	97.95% <100.00%> (+<0.01%)	⬆️
OS-Linux	97.66% <100.00%> (+<0.01%)	⬆️
OS-Windows	94.58% <100.00%> (+<0.01%)	⬆️
OS-macOS	96.78% <100.00%> (-0.01%)	⬇️
Py-3.10.11	96.63% <100.00%> (+<0.01%)	⬆️
Py-3.10.15	97.20% <100.00%> (+0.03%)	⬆️
Py-3.11.10	97.23% <100.00%> (-0.01%)	⬇️
Py-3.11.9	96.69% <100.00%> (-0.01%)	⬇️
Py-3.12.7	97.72% <100.00%> (-0.01%)	⬇️
Py-3.13.0	96.56% <100.00%> (+<0.01%)	⬆️
Py-3.13.1	97.64% <100.00%> (-0.05%)	⬇️
Py-3.9.13	96.55% <100.00%> (+<0.01%)	⬆️
Py-3.9.20	97.12% <100.00%> (+0.03%)	⬆️
Py-pypy7.3.16	96.70% <100.00%> (+<0.01%)	⬆️
VM-macos	96.78% <100.00%> (-0.01%)	⬇️
VM-ubuntu	97.66% <100.00%> (+<0.01%)	⬆️
VM-windows	94.58% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.