Add NTIA validation to self-validation suite

[Copilot]

• Create ValidateNtia.cs to validate NTIA checking functionality
• Update Validate.cs to call ValidateNtia.Run() in the self-validation tests
• Update SelfValidationTests.cs to verify the new NTIA validation test in TRX results
• Run self-validation to verify the new test works correctly
• Run full test suite to ensure no regressions
• Code review completed with no blocking issues
• CodeQL security scan completed with no vulnerabilities
• Refactor DoValidate into DoValidateMissingSupplier and DoValidateCompliant
• Add log output verification to check for specific NTIA error message
• Add clarifying comment about log file path behavior

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add self-validation of NTIA validation</issue_title>
<issue_description>Self-validation is supposed to provide evidence of core functionality, and part of the core functionality is that SpdxTool is capable of performing NTIA validation checks.

An additional self-validation check should be added that verifies NTIA checks can be performed - possibly by having the test write a valid SPDX that isn't NTIA compliant (e.g. missing root packages, missing package supplier, missing package version) and validating the tool reports those failures.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add self-validation of NTIA validation #81

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