Remove RestSharp and WebSocket4Net from Arke.ARI and replace with .NET 6 libraries.

[seiggy]

Transition the library from .NET Standard to .NET 6 in order to migrate off the RestSharp and WebSocket4Net dependencies. Refactor and replace both libraries with native code.

[seiggy]

@nakchak I'm starting to look at removing RestSharp. I definitely want to build in support for both ILogger and IHttpClientFactory to get enhancements such as Polly support out of the box. I think I'm also going to remove support for non-async methods, and migrate the entire event system to fully async out of the box. Just cut some dead weight from the project and code base while I'm at it. I might keep around the ThreadPoolDispatcher, but the DedicatedThreadDispatcher is gone for sure.