State sync 0 - Blocks backfilling option

[abi87]

Why this should be merged

Counterpar of https://github.com/ava-labs/avalanchego/pull/2343, just extending state syncable vm interface. Actual implementation deferred to https://github.com/ava-labs/coreth/pull/353 to ease up code review across repos

How this works

Just empty implementation of new methods requested by the vm interface

How this was tested

CI + successful mainnet sync with https://github.com/ava-labs/avalanchego/pull/2273 code