Investigate Fuel indexer and how we can use it in the agents for observing logs

[tkporter]

• Fuel ships an indexer https://github.com/FuelLabs/fuel-indexer
• Is this our best bet for observing logs in the relayer? Are there any alternatives, e.g. an equivalent of eth_getLogs?
• Should we use the indexer as a Rust dependency and run the indexer that way? Or should we spin up a single indexer binary? Is there an existing public indexer operated by someone else that we can use instead?

[tkporter]

Considering this done