Allow multiple debug connections in VS code using the same port

[udgithub]

Hello debugpy team, hi Pavel,

the discussion
"How to debug cmdline scripts with options used in a sequence of piped cmds with VS Code" #1498
described a way to debug multiple calls of a cmdline script in a sequence of linux commands using a pipe.
In this example the debug connection has been opened from the script to a listening VS code IDE using --connect

If we have a sequence of calls like so
cat myfile | python -m debugpy --connect 5678 ./python-script-1.py --option1=x | python -m debugpy --connect 5679 python-script-2.py --option2=y
we have to use several ports and we have to start several debug sessions in VS code using their own debug settings for each port.
It would be better, if VS code would only need one debug config for multiple incoming connections and could handle them.
Example:

            "name": "Python: Listen 5678",
            "type": "python",
            "request": "attach",
            "listen": {
                "host": "localhost",
                "port": 5678,
                "allow_multiple_connections": "true"    *** NEW ***
            },
        },

This behaviour would be similar to PHP debugging using xdebug and VS code or PHPstrom.

Thanks a lot in advance for realizing this perhaps in the future.

Best regards, Uwe