• Add SubjectAlternativeName property to the Signature class in MshSignature.cs
• Extract SubjectAlternativeName from the SignerCertificate extensions using X509 APIs
• Format the SAN extension similar to the PowerShell example code provided
• Add comprehensive tests to verify the SubjectAlternativeName property
  • Test with certificate containing SAN extension (verifies actual content)
  • Test with certificate without SAN extension (verifies null value)
  • Fixed hanging test by using PSSession with LocalMachine stores
  • Use standard PowerShell pattern for array type checking: ,$result | Should -BeOfType [string[]]
  • Use Should -BeExactly for precise array element validation at specific indices
• Revert unrelated build infrastructure and documentation changes
• Remove nullable reference type annotations (file doesn't have nullable enabled)
• Use named constant for SubjectAlternativeName OID
• Remove obvious comments
• Change SubjectAlternativeName to string array with each line as separate element
• Reverted commit 391245e to restore splitting logic (extension.Format returns string, not string[])
• Updated to handle all line separator types (\r\n, \n, \r) for cross-platform compatibility
• Removed redundant null check (GetSubjectAlternativeName already handles null)

Summary

This PR adds a SubjectAlternativeName property to the Signature class returned by Get-AuthenticodeSignature. The implementation:

1. Core Change: Added a string[] property that extracts the SAN extension (OID 2.5.29.17) from the signer certificate
2. Helper Method: Implements GetSubjectAlternativeName() that searches for and formats the SAN extension using a named constant, then splits it into individual array elements (one per line) using all common line separators for cross-platform compatibility. Handles null certificates gracefully.
3. Comprehensive Tests:
   • Test that verifies certificates WITH SAN content show the expected DNS names as array elements
   • Test that verifies certificates WITHOUT SAN content return null
   • Tests use PSSession with LocalMachine stores to avoid hanging issues
   • Tests use standard PowerShell pattern for array type checking with comma operator
   • Tests use Should -BeExactly for precise validation of array element values at specific indices

The implementation follows the C# translation of the PowerShell example code provided in the issue and maintains backward compatibility.

Fixes #14006

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