Add upload-sarif input to make GitHub code scanning upload optional

[Copilot]

The action always attempted SARIF upload to GitHub code scanning, which fails in repositories without GHAS. This PR adds an explicit opt-out so users can still run InspectCode and keep the report artifact without requiring Advanced Security.

• Action behavior

  • Added new input: upload-sarif (default: true)
  • Updated SARIF upload step condition to require both:
    • format == 'Sarif'
    • upload-sarif == 'true'
  • Preserves current default behavior while enabling GHAS-free usage.

• Documentation

  • Added upload-sarif to the configuration table.
  • Updated usage example to show disabling upload.
  • Clarified that security-events: write is unnecessary when SARIF upload is disabled.

• CI smoke workflow

  • Updated smoke test invocation to run with format: "Sarif" and upload-sarif: "false" so the new path is exercised.

- uses: JetBrains/ReSharper-InspectCode@v0.13
  with:
    solution: ./YourSolution.sln
    format: Sarif
    upload-sarif: false