Support for `multipleOf` schema assertion from `@Digits` BV constraint

There seems to be an opportunity to specify that the `@Digits` BV contraint results in a `multipleOf` assertion in schemas generated from properties with the annotation. We should investigate adding this to the spec and testing the behavior in the TCK.

Original request in smallrye-open-api: https://github.com/smallrye/smallrye-open-api/issues/2384