LEVM: get_state_transitions for the ef-tests

[fborello-lambda]

We had the get_state_transitions function triplicated. With #1949 we centralize the code in one function. However, there is a problem when we use the function when running the ef-tests, a specific computation is performed depending on the fork (line).

If we get the fork from the block's timestamp:

let block_header = current_db
    .get_block_header_by_hash(block_hash)?
    .ok_or(StoreError::MissingStore)?;
let fork_from_config = initial_state.chain_config()?.fork(block_header.timestamp);

it differs from the fork passed as variable in the ef-tests' runners.

I've added an Option<Fork> as function argument: ef_tests: Option<Fork>. It works for now, but we should find a better way and why the fork differs. May have something to do with the genesis used