Clean up CompositeMLDsaAlgorithm and add comprehensive tests

[Copilot]

This PR addresses the cleanup and testing requirements for CompositeMLDsaAlgorithm as requested in the issue.

Changes Made

1. Documentation Fix

• Fixed typo in CompositeMLDsaAlgorithm.cs line 21: "An a string" → "A string"

2. Comprehensive Test Suite

Added CompositeMLDsaAlgorithmTests.cs with tests covering:

• Algorithm parameter validation: Verifies correct names and signature sizes for all 18 composite algorithm variants
• Reference equality: Tests that static properties return the same instances
• Equality/inequality operators: Validates == and != operator behavior
• Hash codes: Ensures consistent GetHashCode() implementation
• String representation: Tests ToString() method
• Null handling: Validates Equals() method with null inputs

3. Test Coverage

The test suite comprehensively covers all 18 CompositeMLDsaAlgorithm variants:

ML-DSA-44 (4 variants):

• MLDsa44WithRSA2048Pss
• MLDsa44WithRSA2048Pkcs15
• MLDsa44WithEd25519
• MLDsa44WithECDsaP256

ML-DSA-65 (8 variants):

• MLDsa65WithRSA3072Pss/Pkcs15
• MLDsa65WithRSA4096Pss/Pkcs15
• MLDsa65WithECDsaP256/P384/BrainpoolP256r1
• MLDsa65WithEd25519

ML-DSA-87 (6 variants):

• MLDsa87WithECDsaP384/BrainpoolP384r1/P521
• MLDsa87WithEd448
• MLDsa87WithRSA3072Pss/RSA4096Pss

4. Integration

• Added tests to both System.Security.Cryptography.Tests.csproj and Microsoft.Bcl.Cryptography.Tests.csproj
• Follows existing patterns from SlhDsaAlgorithmTests and MLDsaAlgorithmTests
• Uses standard xUnit patterns with [Theory], [MemberData], and AssertExtensions

All changes are minimal and surgical, maintaining compatibility while providing comprehensive test coverage for the CompositeMLDsaAlgorithm class.

Fixes #117134.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• http://www.microsoft.com:80/pki/certs/MicCodSigPCA_08-31-2010.crt
  • Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Security.Cryptography.Tests.runtimeconfig.json --depsfile System.Security.Cryptography.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.2-beta.25311.107/build/../tools/net/xunit.console.dll System.Security.Cryptography.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (http block)
• http://www.microsoft.com:80/pki/mscorp/Microsoft%20RSA%20TLS%20CA%2001.crt
  • Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Security.Cryptography.Tests.runtimeconfig.json --depsfile System.Security.Cryptography.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.2-beta.25311.107/build/../tools/net/xunit.console.dll System.Security.Cryptography.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (http block)
  • Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig /home/REDACTED/work/runtime/runtime/artifacts/bin/System.Security.Cryptography.Tests/Debug/net10.0-unix/System.Security.Cryptography.Tests.runtimeconfig.json --depsfile /home/REDACTED/work/runtime/runtime/artifacts/bin/System.Security.Cryptography.Tests/Debug/net10.0-unix/System.Security.Cryptography.Tests.deps.json /home/REDACTED/work/runtime/runtime/artifacts/bin/System.Security.Cryptography.Tests/Debug/net10.0-unix/testhost.dll --port 35095 --endpoint 127.0.0.1:035095 --role client --parentprocessid 73784 --datacollectionport 32835 --telemetryoptedin false (http block)
  • Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig /home/REDACTED/work/runtime/runtime/artifacts/bin/System.Security.Cryptography.Tests/Debug/net10.0-unix/System.Security.Cryptography.Tests.runtimeconfig.json --depsfile /home/REDACTED/work/runtime/runtime/artifacts/bin/System.Security.Cryptography.Tests/Debug/net10.0-unix/System.Security.Cryptography.Tests.deps.json /home/REDACTED/work/runtime/runtime/artifacts/bin/System.Security.Cryptography.Tests/Debug/net10.0-unix/testhost.dll --port 41119 --endpoint 127.0.0.1:041119 --role client --parentprocessid 73986 --datacollectionport 33619 --telemetryoptedin false (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list

---

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[Copilot]

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• http://www.microsoft.com:80/pki/mscorp/Microsoft%20RSA%20TLS%20CA%2001.crt
  • Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig /home/REDACTED/work/runtime/runtime/artifacts/bin/System.Security.Cryptography.Tests/Debug/net10.0-unix/System.Security.Cryptography.Tests.runtimeconfig.json --depsfile /home/REDACTED/work/runtime/runtime/artifacts/bin/System.Security.Cryptography.Tests/Debug/net10.0-unix/System.Security.Cryptography.Tests.deps.json /home/REDACTED/work/runtime/runtime/artifacts/bin/System.Security.Cryptography.Tests/Debug/net10.0-unix/testhost.dll --port 38729 --endpoint 127.0.0.1:038729 --role client --parentprocessid 36858 --datacollectionport 44825 --telemetryoptedin false (http block)
  • Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig /home/REDACTED/work/runtime/runtime/artifacts/bin/System.Security.Cryptography.Tests/Debug/net10.0-unix/System.Security.Cryptography.Tests.runtimeconfig.json --depsfile /home/REDACTED/work/runtime/runtime/artifacts/bin/System.Security.Cryptography.Tests/Debug/net10.0-unix/System.Security.Cryptography.Tests.deps.json /home/REDACTED/work/runtime/runtime/artifacts/bin/System.Security.Cryptography.Tests/Debug/net10.0-unix/testhost.dll --port 37153 --endpoint 127.0.0.1:037153 --role client --parentprocessid 37064 --datacollectionport 43147 --telemetryoptedin false (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list

[dotnet-policy-service]

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