Migrate to Scala 3

[propensive]

With the exception of the property and web modules (which are still work-in-progress), there should be nothing to stop Probably running on Scala 3, but it may need some migration. Arnold de Vos (@arnolddevos) has already put some work into this, but a bit more work is required to make everything work. We need to look at his pull request and make the necessary changes to enable it to be merged and published.