Fix for TLS 1.3 session resumption on Linux

[multiarc]

Fixes #123238

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[rzikm]

LGTM, Thanks!

[Copilot]

Pull request overview

This PR fixes a regression in TLS 1.3 session resumption on Linux where resumed connections with client certificates incorrectly report IsMutuallyAuthenticated=false and LocalCertificate=null. The issue was introduced in a previous commit that added support for TLS resumption with client certificates.

Changes:

• Added a regression test that verifies mutual authentication is correctly reported across multiple TLS connections (including resumed ones)
• Added IntPtr overloads for SslSessionReused and SslGetSession interop methods to support the fix
• Fixed NewSessionCallback in Interop.OpenSsl.cs to inherit certificate information from the current session when TLS 1.3 issues new session tickets on resumed connections

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
SslStreamMutualAuthenticationTest.cs	Added regression test SslStream_Tls13ResumptionWithClientCert_IsMutuallyAuthenticatedTrue that verifies mutual authentication properties are correctly set across initial and resumed TLS connections
Interop.Ssl.cs	Added IntPtr overloads for SslSessionReused and SslGetSession methods to enable calling these functions from unmanaged callback contexts
Interop.OpenSsl.cs	Fixed NewSessionCallback to retrieve certificate information from the current session when TLS 1.3 issues new tickets on resumed connections (when SSL_get_certificate returns null)