Other changes:
* Add server getBlockV2(), and produceBlockV2().
* Add getBlockV2() to REST test suite.
* Add client getBlockV2(), and produceBlockV2().
* Fix URLs in comments.
* Add some primitives and fix some issues in forks.nim.
* Switch `validator_client` to V2 calls usage.
* Bump `chronos` with imports fixes.
* Bump `nim-json-serialization` for `requireAllFields`.