[release/6.0] Add System.Net.Http ServerCertificateCustomValidationCallback ILLink Suppression

[github-actions]

Backport of #58456 to release/6.0

Fixes #57537

During PR #57555, it was unclear what the correct suppression syntax would be for a return type of Func<HttpRequestMessage, X509Certificate2?, X509Chain?, SslPolicyErrors, bool>. With some helpful switches to generate the right warning suppression syntax via --generate-warning-suppressions xml in RuntimePackILLinkArgs, this PR adds the correct warning suppression.

/cc @mdh1418

Customer Impact

When supporting either using the native HttpMessageHandler types in Xamarin or SocketsHttpHandler as the underlying handler in HttpClientHandler, some APIs such as ServerCertificateCustomValidationCallback had thrown PNSE when the native handler was enabled. It didn't make sense to always throw PNSE, and a majority of the methods were modified to suppress ILLink error messages except for ServerCertificateCustomValidationCallback because of its return type.

Removes PNSE from ServerCertificateCustomValidationCallback
Adds ILLink error message suppression for ServerCertificateCustomValidationCallback

Without this PR, ServerCertificateCustomValidationCallback will continue to throw PNSE.

Testing

Risk

Low, this PR will reenable ServerCertificateCustomValidationCallback instead of throwing Arg_PlatformNotSupported exception.

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Issue Details

---

Backport of #58456 to release/6.0

/cc @mdh1418

Customer Impact

Testing

Risk

Author:	github-actions[bot]
Assignees:	-
Labels:	area-System.Net.Http
Milestone:	-

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Tagging subscribers to 'arch-android': @steveisok, @akoeplinger
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Backport of #58456 to release/6.0

Fixes #57537

During PR #57555, it was unclear what the correct suppression syntax would be for a return type of Func<HttpRequestMessage, X509Certificate2?, X509Chain?, SslPolicyErrors, bool>. With some helpful switches to generate the right warning suppression syntax via --generate-warning-suppressions xml in RuntimePackILLinkArgs, this PR adds the correct warning suppression.

/cc @mdh1418

Customer Impact

When supporting either using the native HttpMessageHandler types in Xamarin or SocketsHttpHandler as the underlying handler in HttpClientHandler, some APIs such as ServerCertificateCustomValidationCallback had thrown PNSE when the native handler was enabled. It didn't make sense to always throw PNSE, and a majority of the methods were modified to suppress ILLink error messages except for ServerCertificateCustomValidationCallback because of its return type.

Removes PNSE from ServerCertificateCustomValidationCallback
Adds ILLink error message suppression for ServerCertificateCustomValidationCallback

Without this PR, ServerCertificateCustomValidationCallback will continue to throw PNSE.

Testing

Risk

Low, this PR will reenable ServerCertificateCustomValidationCallback instead of throwing Arg_PlatformNotSupported exception.

Author:	github-actions[bot]
Assignees:	-
Labels:	area-System.Net.Http, os-android
Milestone:	-

[marek-safar]

@mdh1418 this needs more work to fix the build

[lewing]

is this ready now?