Restructuring Socket/TCP conceptual docs

[liveans]

https://learn.microsoft.com/en-us/dotnet/fundamentals/networking/sockets/sockets-overview

Describe the tasks

In an offline discussion with @antonfirsov @dotnet/ncl team, we have decided to do following tasks on conceptual docs:

• Repurpose Use Sockets to send and receive data as Use Sockets to send and receive data over TCP.
• Merge all content under TCP as Use TcpClient and TcpListener and move it under the Sockets.
• Add a remark to Use TcpClient and TcpListener, that we recommend using Socket class directly, instead of it.
• Create an article for UDP (Use Sockets to send and receive data over UDP) (???)
• Create an article to show TcpClient usages equivalent to Socket under Use TcpClient and TcpListener.
• Explain socket states and listening, connecting and accepting.

All other ideas and feedback are appreciated.

CC @dotnet/docs @IEvangelist