Txpool should check for too low nonce against sender

[jangko]

As shown by graphql simulator test result, txpool allow a tx with too low nonce as valid item.
Need to add tx validation in txpool against tx.sender latest state and reject the invalid tx before evm execution.

[jangko]

Turn out this is not a txpool bug, but rather a bug in test or nimbus who is using txpool.
Every test and nimbus should inform txpool with latest valid chain head so it can get correct sender state to compare against incoming txs.