Add equality to MLDsaAlgorithm and add tests

[vcsjones]

MLDsaAlgorithm does not implement equality nor have any tests. Let's fix that.

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[Copilot]

Pull Request Overview

This PR adds value equality support to MLDsaAlgorithm and introduces tests to validate the new behavior.

• Implemented IEquatable<MLDsaAlgorithm>, overrides for Equals, GetHashCode, ToString, and equality/inequality operators in MLDsaAlgorithm.
• Added a DebuggerDisplay attribute for better debugging.
• Created MLDsaAlgorithmTests.cs and wired it into both test projects to cover reference equality, Equals, hash code consistency, operator overloads, and ToString.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/libraries/System.Security.Cryptography/tests/System.Security.Cryptography.Tests.csproj	Included MLDsaAlgorithmTests.cs in test compilation
src/libraries/Microsoft.Bcl.Cryptography/tests/Microsoft.Bcl.Cryptography.Tests.csproj	Included MLDsaAlgorithmTests.cs in test compilation
src/libraries/Common/src/System/Security/Cryptography/MLDsaAlgorithm.cs	Added equality members (IEquatable, overrides, operators), and DebuggerDisplay
src/libraries/Common/tests/System/Security/Cryptography/MLDsaAlgorithmTests.cs	New tests for equality, GetHashCode, operators, and ToString

Comments suppressed due to low confidence (1)

src/libraries/Common/tests/System/Security/Cryptography/MLDsaAlgorithmTests.cs:58

• Consider adding tests for operator == and != when comparing with null (e.g., Assert.True((MLDsaAlgorithm?)null == null) and Assert.True(MLDsaAlgorithm.MLDsa44 != null)), to validate null-handling behavior.

            AssertExtensions.TrueExpression(MLDsaAlgorithm.MLDsa87 != MLDsaAlgorithm.MLDsa44);