fix: Remove deprecated http.CloseNotifier, use Request.Context().Done() in Stream

[haesuo566]

Summary

Fixes #4586

• Remove http.CloseNotifier embedding from the ResponseWriter interface
• Replace w.CloseNotify() with c.Request.Context().Done() in the Stream method
• Update related tests accordingly

Motivation

http.CloseNotifier has been officially deprecated since Go 1.11. The Go documentation recommends using Request.Context() instead:

Deprecated: the CloseNotifier interface predates Go's context package. New code should use Request.Context instead.

Request.Context().Done() also covers a broader set of termination scenarios (timeout, cancellation) beyond just client disconnection.

Changes

response_writer.go

• Remove http.CloseNotifier embedding from the ResponseWriter interface
• Delete the CloseNotify() method from responseWriter

context.go

• Stream: replace clientGone := w.CloseNotify() with clientGone := c.Request.Context().Done()

context_test.go

• Replace closeChannel chan bool + CloseNotify() in TestResponseRecorder with cancel context.CancelFunc
• Update closeClient() to call r.cancel() instead of sending to a channel
• Update CreateTestResponseRecorder() to return (*TestResponseRecorder, *http.Request)
• Update call sites: TestContextStream, TestContextStreamWithClientGone, TestContextResetInHandler

response_writer_test.go

• Remove compile-time interface check for http.CloseNotifier
• Remove w.CloseNotify() panic test block

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.37%. Comparing base (3dc1cd6) to head (3c28f41).
⚠️ Report is 275 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4587      +/-   ##
==========================================
- Coverage   99.21%   98.37%   -0.85%     
==========================================
  Files          42       48       +6     
  Lines        3182     3136      -46     
==========================================
- Hits         3157     3085      -72     
- Misses         17       42      +25     
- Partials        8        9       +1     

Flag	Coverage Δ
	?
--ldflags="-checklinkname=0" -tags sonic	98.36% <100.00%> (?)
-tags go_json	98.29% <100.00%> (?)
-tags nomsgpack	98.35% <100.00%> (?)
go-1.18	?
go-1.19	?
go-1.20	?
go-1.21	?
go-1.25	98.37% <100.00%> (?)
go-1.26	98.37% <100.00%> (?)
macos-latest	98.37% <100.00%> (-0.85%)	⬇️
ubuntu-latest	98.37% <100.00%> (-0.85%)	⬇️

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