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

[MikeEdgar]

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: smallrye/smallrye-open-api#2384