* update ethereumapis dependency
* span
* initial implementation
* introduce stategen Service interface and MockService
* Include AddStateForSlot function in the mock service
* return states from mock
* add GenesisState to POWChain mock
* populate roots in helper state
* initialize Slot when creating helper state
* tests
* code refactor - extract helper functions
* gzl
* use SetSlot in tests
* handle SetSlot error
* use new testutil's NewBeaconState
* gzl
* go mod tidy
* rename Service to StateManager
* move regex check to helper
Co-authored-by: Raul Jordan <raul@prysmaticlabs.com>
Co-authored-by: prylabs-bulldozer[bot] <58059840+prylabs-bulldozer[bot]@users.noreply.github.com>