Adding Abort to C# Websocket

[rekhoff]

Description of Changes

The implementation of a solution to #3044 , this adds an Abort function to the WebSocket, which runs if Disconnect is called when the WebSocket is not connected.

API and ABI breaking changes

Not API breaking.

Expected complexity level and risk

1

Testing

• Test locally with a C# CLI test client.
  Note: Before change (either on Rust of C# server), server would see 4 Debug log entries about connecting, but not see the Info log about the client connection ending like would normally be seen in a disconnect. After change, server shows no log entries at all, because connection is properly aborted.
• Test locally with a C# WebGL test client.

[jdetter]

This is somewhat unrelated but we might want to clean up this logic as well. If the socket isn't in the connected or connecting states we should just not try to disconnect. If the socket is connected we should try a normal disconnection and if the socket is connecting then we should try to abort.

[rekhoff]

More or less that is what this is doing. If DBConnection.Disconnect is called by the client, the Disconnect function is checking if the websocket is connected, and if it isn't actually connected yet, it's calling Abort.
But to your point, I've added a check to ensure we only call Abort if we are in the process of connecting, so we don't accidently call it if we are already disconnecting or are in a closed status.