BCrypt

This file is almost entirely based on https://github.com/t3hnar/scala-bcrypt/tree/master with it's apache-2 license. We have adapted it here for Scala 3 as the project has not yet published a Scala 3 version and looks to be a dead project. We have chosen to remove the old deprecated methods and rename the bounded methods as the old ones - we have complete control over the users of this code (at least where we provide any certainty to them).