fix: address some static code analysis issues, exposed by the latest analyzer

[skwasjer]

• refactor(CA2208): throw invalid enum exception in ctor to satisfy static code analysis.
• fix(SYSLIB0051): mark serializable/binary formatter support as obsolete
• refactor(CA1031): use TryAddWithoutValidation to avoid exceptions and to skip adding header if not supported.
• fix(CA2007): use ConfigureAwait on awaitable async stream
• test(CS8604): in older runtimes, IEqualityComparer<> did not use nullable annotation. Fix with string polyfill for Arg.Any.

[sonarcloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
2 Code Smells

75.0% Coverage
0.0% Duplication

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