Verification: method to decode undecoded event logs

[NikitaSavik]

The new transaction decoding service requires that events emitted during the transaction should be undecoded somehow. Blockscout may undecode event logs only if the contract is verified. We need a service that will look for potential event candidates based only on the raw event data (topics and data encoded).

Currently, we have the sig-provider service, that looks for the potential candidates in 3-rd party services (sigeth and 4bytes, as for now). But those services are too slow and cannot process a large amount of events in adequate time. The idea is to update eth-bytecode-db service to store signatures for the contracts verified through it, and provide an endpoint that will support quick event lookups.

In the applied approach, eth-bytecode-db will only search for the potential event abis based on the event selector and will be similar in its functionality to 4bytes and sigeth. The candidates processing will remain on the sig-provider side

[rimrakhimov]

• Add event signatures into eth-bytecode-db and implements corresponding lookup api endpoint
  Eth-bytecode-db - search event signatures #698
• Add eth-bytecode-db as a source for event abis
  [SIG_PROVIDER] Add eth-bytecode-db source. Add batched event retrievals #707
• Import events from existing eth-bytecode-db abis
  [ETH_BYTECODE_DB] import_abis binary implementation #717