Fix extrinsic params for contract chains

Sergej Kostjucenko requested to merge aj/fix-extrinsic-params into master

Created by: ascjones

Fixes the SignedExtra type to align with substrate-contracts-node and the parachain runtime.

This PR changes it to PolkadotExtrinsicParams which is just an alias to BaseExtrinsicParams<T, PlainTip> which maps to the runtime SignedExtra1 definition with pallet_transaction_payment::ChargeTransactionPayment`

Fixes #515 (closed)

Merge request reports