Add Custom Clients and Servers

[Phillezi]

Add Custom Clients and Servers making TCP/TLS and UDP/DTLS possible

Added the ability to create custom clients and servers that conform to returning net.Listener and net.Conn. This is a useful feature for implementing custom TLS and DTLS communication without requiring external dependencies in this library.

Why would someone want this:

• Customizability: By allowing the creation of custom clients and servers, users of the library can implement custom protocols and are not limited to the TCP and UDP client and server implementations.
• TLS with TCP: This feature allows implementing TLS on top of TCP without the library getting bloated by relying on external dependencies.
• DTLS with UDP: It also makes it possible to implement TLS for UDP by using DTLS, tested using the Pion DTLS library.

Example Usage:

I added an example implementation of a server and client that uses TCP/TLS in the examples/ dir,

• client
• server

Let me know if you would like any changes made : )

[codecov]

Codecov Report

❌ Patch coverage is 25.75758% with 49 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.95%. Comparing base (6c20857) to head (bdd40a8).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
endpoint_client.go	27.77%	25 Missing and 1 partial ⚠️
endpoint_server.go	23.33%	23 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #175      +/-   ##
==========================================
- Coverage   81.46%   80.95%   -0.52%     
==========================================
  Files         705      705              
  Lines        8266     8312      +46     
==========================================
- Hits         6734     6729       -5     
- Misses        917      967      +50     
- Partials      615      616       +1     

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[aler9]

This looks good, furthermore i think it can entirely replace the former EndpointCustom and be used as parent for serial and broadcast endpoints. Merged, thanks!