[Keep Alive] [C#] Client timeout on idle server

[analogrelay]

Once #1156 is implemented, the client can implement a "minimum data rate" timeout where if the server hasn't sent a message within a certain window, it will terminate the connection and report that back to the application. This allows applications to detect network failures without relying on OS-specific transport timeouts. This should be configurable, since it depends on how frequently the server is sending Ping messages.

This issue will track C# implementation of this behavior. #1162 tracks JavaScript implementation.

Related: #1156