Make Pkcs12LoaderLimits.AllowDuplicateAttributes public

[vcsjones]

Closes #117516

[Copilot]

Pull Request Overview

This PR makes the AllowDuplicateAttributes property of the Pkcs12LoaderLimits class public, addressing issue #117516. This change provides users with more granular control over PKCS#12 loading behavior without requiring them to use the DangerousNoLimits setting.

Key changes:

• Exposed the AllowDuplicateAttributes property as public API
• Updated test code to use the newly public property instead of relying on DangerousNoLimits
• Added the property to the reference assembly

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/libraries/System.Security.Cryptography/ref/System.Security.Cryptography.cs	Added public AllowDuplicateAttributes property to the reference assembly
src/libraries/Common/src/System/Security/Cryptography/X509Certificates/Pkcs12LoaderLimits.cs	Changed visibility of AllowDuplicateAttributes property from internal to public
src/libraries/Common/tests/System/Security/Cryptography/X509Certificates/X509CertificateLoaderPkcs12Tests.cs	Updated test to use the public property directly instead of conditional logic with DangerousNoLimits
src/libraries/Common/tests/System/Security/Cryptography/X509Certificates/X509CertificateLoaderPkcs12CollectionTests.cs	Updated test to use the public property directly instead of conditional logic with DangerousNoLimits

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[vcsjones]

@bartonjs I don't think we can OOB this for < .NET 10. Since the loader limit is a type forward for .NET 9, we can't make it public in the .NET 9 build but have it type forward to in in-box one that is still internal.

[bartonjs]

Good catch on the OOB.

[vcsjones]

/ba-g Android time out is dotnet/dnceng#5909. The lane was disabled in #117703 but this pull request was in between the known issue and the lane getting disabled.