Have clear intent about enum attribute of any validator when calling directly

[nohponex]

Because all validators support the enum attribute, it is now clear to library end-users what will happen with it.

phramework/jsonapi has a separate (custom) EnumValidator and "type": "enum", which essential is the same as having "enum": [...] inside the schema.

So for users that are used or know JSON to any ValidatorFiller besides the EnumValidatorFiller` it will ignore the enum attribute.

Initial design and intent was to, intercept the presence of enum attribute at FillerRepository->fill and redirect/use it with EnumValidatorFiller implementation of returning a random item