Enhanced listener/callback functionality for processing guardian

[mattsmithies]

Overview

As the Guardian defers writing to blocks (depending on environment), there is a requirement to add sleep/timeouts into the code itself.

Previously inside of tests, we had created callback functionality that would listen for particular states to change before fetching data, but this needs to be enhanced for when blocks are filtered upon before making requests.

Using timeouts/sleep functionality is inconsistent, especially in testnet/mainnet conditions.