Implement all read-only eth_* json-rpc methods

[carver]

• support core eth_* read-only methods
  • eth_protocolVersion
  • eth_syncing
  • eth_gasPrice (should get its own issue to plan the algorithm)
  • eth_blockNumber
  • eth_getBalance
  • eth_getStorageAt
  • eth_getTransactionCount
  • eth_getBlockTransactionCountByHash
  • eth_getBlockTransactionCountByNumber
  • eth_getUncleCountByBlockHash
  • eth_getUncleCountByBlockNumber block int
  • eth_getUncleCountByBlockNumber block string
  • eth_getCode
  • eth_call
  • eth_estimateGas
  • eth_getBlockByHash
  • eth_getBlockByNumber block int
  • eth_getBlockByNumber block string
  • eth_getTransactionByHash
  • eth_getTransactionByBlockHashAndIndex
  • eth_getTransactionByBlockNumberAndIndex
  • eth_getTransactionReceipt
  • eth_getUncleByBlockHashAndIndex
  • eth_getUncleByBlockNumberAndIndex block int
  • eth_getUncleByBlockNumberAndIndex block string
  • eth_getCompilers (deprecated)
  • eth_getLogs
• support mining eth_* read-only methods
  • eth_coinbase (returns error with: Trinity does not support mining)
  • eth_hashrate (returns error with: Trinity does not support mining)
  • eth_mining (returns False since Trinity does not support mining)
  • eth_getWork (returns error with: Trinity does not support mining)
• endpoints that trinity will not support
  • eth_accounts (Trinity will always reply with [])
• make score available on block object, so that a returned block dict can be formatted without a chain reference ?

[carver]

So the three remaining are:

• eth_gasPrice -- I'd say it's hard enough to do well, that we should just leave unimplemented until EIP 1559, which significantly simplifies it
• eth_getLogs -- intentionally punting filters for now
• trying to refactor away the chain reference? I think that's not going to happen, it was a pipe dream, born during the earliest/simplest command implementations

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Which means I think we can close this? I'm going to be a little optimistic here and close it. I'm happy to re-open if anyone objects, of course.