Apply bal without executing block for finalized blocks

[bhartnett]

As a sync optimization we can skip executing the block when we have a block access list available for a finalized block. In this case we simply apply the BAL and then persist the ledger changes without executing the transactions.

The function which applies the BAL to the state, loops through each account and writes the last update for each type of change (balance, nonce, code, storage). This should be much faster than executing the full block.

This feature is also used when replaying blocks on startup which should speed up that part which was previously rather slow.

[bhartnett]

One problem with this optimization is that receipts cannot be generated without executing the block and so this idea may not be viable if we want to support querying historical receipts via JSON-RPC.