* more fork-choice fixes
* use target block/epoch to validate attestations
* make addLocalValidators sync
* add current and previous epoch to cache before doing state transition
* update head state using clearance state as a shortcut, when possible
* use blockslot for fork choice balances
* send attestations using epochref cache
* fix invalid finalized parent being used
also simplify epoch block traversal
* single error handling style in fork choice
* import fix, remove unused async