After a lot of discussion with reddit and friends, it seems that deprecating rustup install and rustup uninstall would have consequences I'd not considered (printed books) and as such it'd be unpleasantly surprising for new users to be told the book they bought was wrong.

As such, we should demote the deprecation warning code from warn!() to verbose!() and make it clear that the reason for the message is that until true alias support is added, these may not function quite as the toolchain XXX commands would.

Long-term we want to replace the deprecated subcommands with true aliases so that this can't be a problem again in the future.