[Bug] [csharp-netcore] WebClient not supported in Blazor WebAssembly

Try to support Blazor WASM with generators

• The Restsharp uses the webclient, WebClient cannot be used on the Browser (client-side Blazor) simply because it is relatively old technology, and there is no reason to adapt it to use on the browser.

System.Net.Requests is not supported on this platform.
System.PlatformNotSupportedException
System.Net.Requests is not supported on this platform.
at System.Net.WebRequest.get_DefaultWebProxy()
at RestSharp.RestClient.ConfigureHttp(IRestRequest request)
at RestSharp.RestClient.ExecuteAsync(IRestRequest request, Action2 callback, String httpMethod, Func4 getWebRequest)
at RestSharp.RestClient.ExecuteAsync(IRestRequest request, Action2 callback, Method httpMethod) at RestSharp.RestClient.ExecuteAsync(IRestRequest request, Action2 callback)
at RestSharp.RestClient.ExecuteAsync[CourseDTOPaginatedList](IRestRequest request, Action`2 callback)
at RestSharp.RestClient.ExecuteAsync[CourseDTOPaginatedList](IRestRequest request, CancellationToken cancellationToken)
--- End of stack trace from previous location ---

Start from the generated C# .NET client path and the RestSharp.RestClient.ConfigureHttp call shown in the stack trace. Reproduce the client in Blazor WebAssembly and trace the WebClient usage; done means requests work in the browser without System.PlatformNotSupportedException.