Idea: Single flag to enable all warnings/errors #2376

I'm working on a code base where we have all the warning and error flags on, and want to keep our code as clean as possible. Recently, a new warning flag was added (--warn-no-return), which I only happened to find out about. It would be awesome if there was some rollup flag that new warnings/errors are added to (some sort of --strictest or --all-warnings-errors) so I could be confident that mypy is using the strictest checks it offers without having to continuously check back in on what flags are available.