Commtiment: Use StateReader instead of PatriciaContext

[awskii]

We do use some intermediate structure for reading state by trie: PatriciaContext.
Basically, if we make StateReader interface to be used instead, patricia trie could be used together with any implementation of reader which we have plenty.

Another point is that account serializing #13390 relying on account.Account type which may be used inside account cells instead of bunch of fields (eg balance, nonce, etc) for sake of consistency.
Also gives us ability to keep account node storage root which we discard after hashing of account node with storage subtrie. This root is useful during Proof and Witness building.