Remove `http.server.CGIHTTPRequestHandler` and `--cgi` flag support

[picnixz]

Feature or enhancement

Proposal:

This class is insecure, barely used and as we said "Anything is better than CGI to interface a web server with a request handler".

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-133810: remove http.server.CGIHTTPRequestHandler and --cgi flag #133811