[csharp] Update to GenHTTP 9.6 and use a regular handler for JSON#9568

NateBrady23 merged 3 commits intoTechEmpower:masterTechEmpower/FrameworkBenchmarks:masterfrom

Kaliumhexacyanoferrat:genhttp-9.6Kaliumhexacyanoferrat/FrameworkBenchmarks:genhttp-9.6Copy head branch name to clipboard