BREAKING: All items except for main() are now private by default,
  and only available when the `experimental-api` feature is enabled.
BREAKING: The deprecated features `memquota` and `dialoguer`
  (which did nothing) are now removed.
BREAKING: The aliases `signal-hook` and `signal-hook-async-std`
  (deprecated aliases for async-signal) are now removed.
BREAKING(CONFIG!!): Removed the deprecated 'proxy.socks_port' option,
  which has been superseded by `proxy.socks_listen` for several years.
BREAKING(CONFIG!!): Removed the deprecated 'proxy.dns_port' option,
  which has been superseded by `proxy.dns_listen` for several years.
