Replace ad-hoc test_ssl threaded server with ThreadedTCPServer

[arhadthedev]

[arhadthedev]

• replace adhoc test servers with ThreadedTCPServer/ThreadedTCPRequestHandler

• https://peps.python.org/pep-0594/:

  Andrew Svetlov mentioned the socketserver module is questionable. However it’s used to implement http.server and xmlrpc.server. The stdlib doesn’t have a replacement for the servers, yet.

  So this PR gives a new, useful life to the module.

• How to implement: https://docs.python.org/3/library/socketserver.html#asynchronous-mixins

[arhadthedev]

ThreadedTCPServer still requires manual creation of a server thread. Its threaded nature is in creation of a thread for each individual client. So closing.

[arhadthedev]

The test_ssl actually uses this threaded model. Reopening.

[arhadthedev]

The issue is postponed because the changes broke tests, and I couldn't find why yet. The changes live in
https://github.com/python/cpython/compare/3f61db475692511a9676765e6f9f0bb204306e93...arhadthedev:threadedserver?expand=1.

[arhadthedev]

The issue is postponed

Fixed, so CPython PR 92475 is ready to be merged.