Use login-profile existence on AWS users to determine whether user is human

[eversC]

in rotatekeys.go, we currently use regex to determine whether a user is human or not:

//validAwsKey returns a bool that reflects whether the provided keys.Key is
// valid, based on aws-specific rules
func validAwsKey(key keys.Key, config config.Config) (valid bool) {
	if config.IncludeAwsUserKeys {
		valid = true
	} else {
		match, _ := regexp.MatchString("[a-zA-Z]\\.[a-zA-Z]", key.Name)
		valid = !match
	}
	return
}

we should instead determine this from the existence of a login-profile for the user. Potentially this