feat(http-client-csharp): adopt TCGC getAllOperations (#3867)

- update emitter logic to derive operation definitions from TCGC instead
of raw compiler output
- temporarily work around the mis-use of `InputParameter.DefaultValue`
for constant values
- add conversion from `InputLiteralType.Value` to
`InputParameter.DefaultValue` in converter
- add implicit conversion operation from `InputLiteralType` to
`InputConstant`
- update unit test cases
- minor error message improvement

part of Azure/autorest.csharp#3994

---------

Co-authored-by: Mingzhe Huang (from Dev Box) <[email protected]>

packages/http-client-csharp/emitter/src/lib/converter.ts

@@ -52,6 +52,7 @@ export function fromSdkType(
     } as InputNullableType;
   }
   if (sdkType.kind === "model") return fromSdkModelType(sdkType, context, models, enums);
+  if (sdkType.kind === "endpoint") return fromSdkEndpointType();
   if (sdkType.kind === "enum") return fromSdkEnumType(sdkType, context, enums);
   if (sdkType.kind === "enumvalue")
     return fromSdkEnumValueTypeToConstantType(sdkType, context, enums, literalTypeContext);
@@ -64,10 +65,9 @@ export function fromSdkType(
     return fromSdkDateTimeType(sdkType);
   if (sdkType.kind === "duration") return fromSdkDurationType(sdkType as SdkDurationType);
   if (sdkType.kind === "tuple") return fromTupleType();
-  // TODO -- only in operations we could have these types, considering we did not adopt getAllOperations from TCGC yet, this should be fine.
-  // we need to resolve these conversions when we adopt getAllOperations
+  // TODO -- endpoint and credential are handled separately in emitter, since we have specific locations for them in input model.
+  // We can handle unify the way we handle them in the future, probably by chaning the input model schema and do the conversion in generator.
   if (sdkType.kind === "credential") throw new Error("Credential type is not supported yet.");
-  if (sdkType.kind === "endpoint") throw new Error("Endpoint type is not supported yet.");
 
   return fromSdkBuiltInType(sdkType);
 }
@@ -368,3 +368,9 @@ function fromSdkArrayType(
     CrossLanguageDefinitionId: arrayType.crossLanguageDefinitionId,
   };
 }
+
+function fromSdkEndpointType(): InputPrimitiveType {
+  return {
+    Kind: "string",
+  };
+}