[CI Postmortem] Flaky tests confirmed by rerun: network/TLS tests on macOS

[rolfbjarne]

Summary

Several network-related tests were confirmed flaky by rerun recovery on PR #25183 (same commit 3a0e9a9f):

Flaky Tests

1. MonoTests.System.Net.Http.MessageHandlerTest.TestNSUrlSessionHandlerSendClientCertificate

• Failed in 13884667, passed in 13884678
• Suite: monotouch-test (macOS)

2. MonoTouchFixtures.Security.SecureTransportTest.Tls12

• Failed in 13884667, passed in 13884678
• Error: System.Net.Sockets.SocketException : Operation timed out [2607:f8b0:400a:801::2003]:443
• Suite: monotouch-test (macOS)

3. MonoTouchFixtures.SystemConfiguration.NetworkReachabilityTest.CtorIPAddressPair

• Failed in 13884667, passed in 13884678
• Suite: monotouch-test (macOS)

Classification

• Type: Flaky (confirmed by rerun)
• Root cause: Network/TLS tests depend on external connectivity and are sensitive to CI agent network conditions

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Filed automatically by CI postmortem analysis.

[rolfbjarne]

Closing — splitting into separate issues per test for easier tracking.