Test interoperability of RAVs between indexer-rs and indexer-agent

[aasseman]

Need to test interoperability of the RAVs saved to the scalar_tap_ravs table by the TAP Agent with the indexer-agent. The indexer-agent is tasked with redeeming the RAVs on-chain against the TAP contract.

• The indexer-agent branch to test: collect tap ravs graphprotocol/indexer#831
• The RAVs are serialized here: https://github.com/graphprotocol/indexer-rs/blob/6c0869776ada0330a77b616cd59fcc944546be77/tap-agent/src/tap/rav_storage_adapter.rs#L29-L52. The code to create a signed RAV is in the tests of that same file.