StateNetwork refactor

[ScottyPoi]

StateNetwork refactor and restructuring

Structure:

• StateNetwork class
  • store, findContentLocally, sendFindContent
  • helper methods for store
    • receive[...]Offer, storeInterested[...]Nodes, forward[...]Offer
  • this.manager: StateManager
• StateManager class
  • State lookup methods matching RPC methods
    • getAccount
    • getStorageAt
    • getCode
    • getBalance, getNonce, etc.
  • this.trie: PortalTrie
• PortalTrie class
  • wrapper methods around trie walking and node lookup
  • find[...]Path(...)
  • lookup[...]TrieNode(...)
  • Fetches nodes with Network Lookup when not found locally
  • this.db: PortalTrieDB
    • Trie database extension that can find nodes in local DB or temporary node cache
• PortalTrieDB class
  • extends DB interface for @ethereumjs/trie
  • this.db hooks directly to local StateNetwork DB
  • this.temp stores path nodes during trie walking
  • this.local maps nodeHash to DB content key for locally stored nodes

--

Distinction between new StateManager class and preexisting UltralightStateManager class

StateManager class is an attribute of StateNetwork. It enables state content lookup via StateNetwork retrieval methods. It exposes methods like getAccount, getCode, and getStorageAt.

UltralightStateManager class implements EVMStateManagerInterface from @ethereumjs/statemanager. It also contains state lookup methods like getAccount and getContractCode, and hooks into the methods provided in state.manager for state lookup.
It also implements state update methods. It can be used to instantiate an EVM during methods like eth_call