Implement skipped acceptance tests

[jhthorsen]

Unfortunately there are some skipped tests in the acceptance tests.

Because of not enough time lately I will document them here in this issue and hope for some pull requests from the community.

• https://github.com/jhthorsen/json-validator/blob/master/t/draft-4-acceptance.t
  • id.json - id inside an enum is not a real identifier
• https://github.com/jhthorsen/json-validator/blob/master/t/draft-6-acceptance.t
  • id.json - id inside an enum is not a real identifier
  • const.json - float and integers are equal up to 64-bit representation limits
• https://github.com/jhthorsen/json-validator/blob/master/t/draft-7-acceptance.t
  • id.json - id inside an enum is not a real identifier
  • const.json - float and integers are equal up to 64-bit representation limits
• https://github.com/jhthorsen/json-validator/blob/master/t/draft2019-09-acceptance.t
  • defs.json - invalid definition
  • defs.json - validate definition against metaschema
  • id.json - $id inside an enum is not a real identifier
  • ref.json - ref creates new scope when adjacent to keywords
  • ref.json - remote ref, containing refs itself 'remote ref invalid
  • anchor.json - $anchor inside an enum is not a real identifier
  • anchor.json - Location-independent identifier with base URI change in subschema
  • refRemote.json remote ref
  • recursiveRef.json
  • unevaluatedItems.json
  • unevaluatedProperties.json

I don't think the "float" related tests can be fixed in Perl, but I'm documenting them anyways.