[FEATURE] Raise `ENEEDAUTH` error if doing a write to something other than login

[isaacs]

If making a PUT/DELETE (and maybe POST?) to any endpoint other than the login endpoints, if auth can't be found in the config, raise an ENEEDAUTH error.

This would allow us to remove some duplicative checks from npm/cli, and also catch any cases we've missed where the user will end up getting a 403 or 401.