Add LRO usage flags (#7370)

Contributes to Azure/azure-sdk-for-net#49632

Author: JoshLove-msft

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.Input/src/InputTypes/InputModelTypeUsage.cs

@@ -19,5 +19,7 @@ public enum InputModelTypeUsage
         Json = 256,
         Xml = 512,
         Exception = 1024,
+        LroInitial = 2048,
+        LroFinalEnvelope = 4096,
     }
 }

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.Input/src/InputTypes/Serialization/TypeSpecInputModelTypeConverter.cs

@@ -105,8 +105,6 @@ internal static InputModelType CreateModelType(ref Utf8JsonReader reader, string
             model.Summary = summary;
             model.Doc = doc;
             var parsedUsage = Enum.TryParse<InputModelTypeUsage>(usageString, ignoreCase: true, out var usage) ? usage : InputModelTypeUsage.None;
-            // TO-DO: Manually add JSON usage flag for now until support for parsing this is added to the TSP https://github.com/microsoft/typespec/issues/3392
-            parsedUsage |= InputModelTypeUsage.Json;
             model.Usage = parsedUsage;
             model.DiscriminatorValue = discriminatorValue;
             model.DiscriminatorProperty = discriminatorProperty;