add support for EDE 7 and 8

add support for EDE 7 and 8

Extended DNS Error messages EDE 7 (expired key) and EDE 8 (validity
period of the key not yet started) are now sent in case of such DNSSEC
validation failures.

Refactor the existing validator extended error APIs in order to make it
easy to have a consisdent extra info (with domain/type) in the various
use case (i.e. when the EDE depends on validator state,
validate_extendederror or when the EDE doesn't depend of any state but
can be called directly in a specific flow).