* Initial commit.
* Fix path.
* Add validator keys to indices cache mechanism.
Move syncComitteeParticipants to common place.
* Fix sync participants order issue.
* Fix error code when state could not be found.
Refactor `state/validators` to use keysToIndices mechanism.
* Fix RestValidatorIndex to ValidatorIndex conversion TODOs.
* Address review comments.
* Fix REST test rules.