perf(continuations): Process state trie at the end

[Nashtare]

#402 is introducing the notion of linked lists for the state trie and moves initial state trie hashing at the end of the execution to remove the burden on memory for prior segments.

This could be pushed further, by changing the tries ordering and processing the state trie after txn & receipt tries. For large batches, this should delay state-related data to be written to memory to later segments.
This may require having state data stored in a decoupled segment than txn / receipt data.