[TEST] Fixes BasicCurlHttpTests.RepeatedCallerThreadCancelsAreClean is flaky

[owent]

Fixes #4510

Changes

• The details are in [TEST] BasicCurlHttpTests.RepeatedCallerThreadCancelsAreClean is flaky #4510 (comment)

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.46%. Comparing base (bc2831a) to head (db240f9).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4524      +/-   ##
==========================================
- Coverage   83.47%   83.46%   -0.00%     
==========================================
  Files         521      521              
  Lines       20380    20380              
==========================================
- Hits        17011    17009       -2     
- Misses       3369     3371       +2     

see 1 file with indirect coverage changes

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[Copilot]

🟢 Approval recommended

The change is small and targeted to test flakiness, with only minor maintainability nits (unused failure counter) noted.

Pull request overview

This PR addresses flakiness in BasicCurlHttpTests.RepeatedCallerThreadCancelsAreClean by ensuring the test’s terminal-notification accounting includes additional failure outcomes that can occur during cancellation/connection-race scenarios in the curl HTTP client tests.

Changes:

• Treat SessionState::ConnectFailed and SessionState::SendFailed as terminal outcomes for TerminalCountingHandler’s terminal counter.
• Add tracking for failure outcomes (currently via a new failed_count_ counter).

File summaries

File	Description
ext/test/http/curl_http_test.cc	Updates TerminalCountingHandler to count connect/send failures as terminal events to stabilize terminal totals in the flaky test scenario.

Review details

Suppressed comments (1)

ext/test/http/curl_http_test.cc:145

• After removing the unused failed_count_ updates, this member can also be removed to keep TerminalCountingHandler minimal.

  std::atomic<int> terminal_count_{0};
  std::atomic<int> cancelled_from_callback_{0};
  std::atomic<int> failed_count_{0};

• Files reviewed: 1/1 changed files
• Comments generated: 1
• Review effort level: Lite

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[marcalff]

Thanks for the root cause analysis and fix.

LGTM, see some cleanup around unused member variable.