State independent verification (Neo 3)

[igormcoelho]

I was thinking, and perhaps having state-related things on Verification would harm TPS anyway. I mean, if we have Storage.Get here, it means that nodes should have complete state in order to verify transactions, and this behavior should change, correct?
Do you think it's too damaging, removing everything state-related from verification now, example, storage access, past notifications, past block access (except for last block), and focus only on things you could immediately access and compute? This is an even stricter view of my other proposal on neo-vm, but I think it's interesting and perhaps necessary for a massive performance.
Clients could still perform timelocks, multisig (with finite loops) and classic verification stuff.

I think this helps PR discussion: #791

And vm issue: neo-project/neo-vm#151

[igormcoelho]

@shargon @erikzhang @vncoelho @jsolman @canesin

[igormcoelho]

Verification cannot be fully state independent, because of NEP-5 transfers. But we can make it partially independent, only depending on few state operations, that don't require precise state updates.