`--debug` flag to pause and print PID for use in debuggers, profilers, etc

Similar to other tools, it would be nice when developing CPython to have a good mechanism for debugging. I think it would be nice to have a --debug flag that when passed, prints something like this Debug Mode PID XXXX Press any key to continue... Then, people could copy the PID and paste it into any debugger, profiler, etc that supports it. I think having the program be executed until after the PID is copied can also be useful. I think having a builtin way of doing this can be very useful to...