[WinHTTP] Certificate caching on WinHttpHandler to eliminate extra call to Custom Certificate Validation

[liveans]

This PR goal is improving performance around CustomCertificateValidationCallback.

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[liveans]

/azp run runtime-libraries-coreclr outerloop-windows

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[rokonec]

This is very nice for Prove of concept, but there are few things which needs to be considered before we decide on feasibility of this approach:

• decide if unbounded cache can be an memory leak issue (I have hard time to imagine use where it would)
• consider different cache key to handle virtual servers infra

[liveans]

/azp run runtime-libraries-coreclr outerloop-windows

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[Copilot]

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

[liveans]

/azp run runtime-libraries-coreclr outerloop-windows

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[liveans]

I'm going to merge this after CI run and I'll track this in CI for a while on main, will start backporting process afterwards.

If you have further concerns with PR, ptal @antonfirsov @wfurt @MihaZupan

[liveans]

/azp run runtime-libraries-coreclr outerloop-windows

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[liveans]

/backport to release/9.0-staging

[github-actions]

Started backporting to release/9.0-staging: https://github.com/dotnet/runtime/actions/runs/14334626247

[github-actions]

@liveans backporting to "release/9.0-staging" failed, the patch most likely resulted in conflicts:

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patch

Applying: Certificate caching on WinHttpHandler to eliminate extra call to Custom Certificate Validation
Applying: Review feedback
Applying: Review feedback
Applying: Framework compat + Review Feedback
Applying: Implement Timer to clear cache
error: sha1 information is lacking or useless (src/libraries/System.Net.Http.WinHttpHandler/src/System/Net/Http/WinHttpHandler.cs).
error: could not build fake ancestor
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0005 Implement Timer to clear cache
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!