Fix endpoint override for .NET SDK generator (#1088)

PR #1082 migrated the C# telemetry generator to AWS SDK V4. Due to
changes in contracts with this version, a Custom PartialConfig file was
added to meet the interface requirements for configuring endpoints with
the ClientConfig. This caused issues during runtime since our client
does not rely on endpoitns. As a workaround as per .NET SDK team's
guidance, since our client always sets the ServiceUrl on out client, a
fix along those lines has been made to short-circuit the underlying
logic and return endpoint based on the service url.

Author: shruti0085

telemetry/csharp/AwsToolkit.Telemetry.SDK/Custom/AmazonToolkitTelemetryConfig.Partial.cs

@@ -31,15 +31,8 @@ public partial class AmazonToolkitTelemetryConfig
         /// <returns>The resolved endpoint for the given request.</returns>
         public override Amazon.Runtime.Endpoints.Endpoint DetermineServiceOperationEndpoint(ServiceOperationEndpointParameters parameters)
         {
-            var request = new DefaultRequest(parameters.Request, ServiceId);
-            request.AlternateEndpoint = parameters.AlternateEndpoint;
-            
-            var requestContext = new RequestContext(false);
-            requestContext.ClientConfig = this;
-            requestContext.OriginalRequest = parameters.Request;
-            requestContext.Request = request;
-            var executionContext = new Amazon.Runtime.Internal.ExecutionContext(requestContext, null);
-            return new BaseEndpointResolver().GetEndpoint(executionContext);
+            var endpoint = new Endpoint(this.ServiceURL);
+            return endpoint;
         }
     }
 }