[csharp] do not use deprecated HttpRequestMessage.Properties (#20737) #249

Job	Run time
Build .Net projects (samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf)	50s
Build .Net projects (samples/client/petstore/csharp/generichost/latest/Tags)	38s
Build .Net projects (samples/client/petstore/csharp/generichost/net9/AllOf)	40s
Build .Net projects (samples/client/petstore/csharp/generichost/latest/HelloWorld)	38s
Build .Net projects (samples/client/petstore/csharp/generichost/latest/OneOfList)	42s
Build .Net projects (samples/client/petstore/csharp/generichost/latest/ComposedEnum)	42s
Build .Net projects (samples/client/petstore/csharp/generichost/net9/AnyOf)	52s
Build .Net projects (samples/client/petstore/csharp/generichost/net9/NullReferenceTypes)	56s
Build .Net projects (samples/client/petstore/csharp/generichost/net9/FormModels)	53s
Build .Net projects (samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare)	41s
Build .Net projects (samples/client/petstore/csharp/restsharp/net9/EnumMappings)	44s
Build .Net projects (samples/client/petstore/csharp/httpclient/net9/Petstore-nonPublicApi)	51s
Build .Net projects (samples/client/petstore/csharp/generichost/net9/Petstore)	49s
Build .Net projects (samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate)	54s
Build .Net projects (samples/client/petstore/csharp/generichost/net9/SourceGeneration)	49s
Build .Net projects (samples/client/petstore/csharp/generichost/net9/OneOf)	47s
Build .Net projects (samples/client/petstore/csharp/httpclient/net9/Petstore)	1m 4s
	13m 30s

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