Tries to load the execution state from DB, returns nil with no error if no state found.

Initialises the validator Ring from the validator storage in forest.

Make genesis state from GenesisDoc and save to DB.

NewState creates a new State object.

Since we have an initial save of our state forest we start one version ahead of the block height, but from then on we should track height by this offset.

This is the immutable merklised read state at a given finalised height.

Writers to state are responsible for calling State.Lock() before calling.