Transaction Payment Module

This module provides the basic logic needed to pay the absolute minimum amount needed for a transaction to be included. This includes:

• weight fee: A fee proportional to amount of weight a transaction consumes.
• length fee: A fee proportional to the encoded length of the transaction.
• tip: An optional tip. Tip increases the priority of the transaction, giving it a higher chance to be included by the transaction queue.

Additionally, this module allows one to configure:

• The mapping between one unit of weight to one unit of fee via [Trait::WeightToFee].
• A means of updating the fee for the next block, via defining a multiplier, based on the final state of the chain at the end of the previous block. This can be configured via [Trait::FeeMultiplierUpdate]