Summary

Currently the code of the mempool reactor makes calls directly to CListMempool's methods that are not part of the Mempool interface. A clear separation of concerns will help introduce future improvements to the gossip protocol in the reactor, to modularize the mempool components, and to have multiple mempool implementations if we need to.

Specifically, in the mempool reactor:

• NewReactor takes a CListMempool as a parameter, instead of an interface Mempool,
• there are calls to implementation specific methods such as TxsWaitChan and TxsFront for iterating through CListMempool's entries, and also to SetLogger,
• there are calls to methods NextWaitChan and Next from mempoolTx, which is the data structure used as entries in the list CListMempool.

DoD

• Define and implement a clear Mempool interface, so that the reactor only interacts with the mempool implementation through the interface methods.