## Description 

1. implement `get_finalized_bridge_action_maybe` in `EthClient`
2. implement simple logic for
`BridgeRequestHandler::handle_eth_tx_hash`. I'm looking to add caching +
NotifyRead-ish thing in a future PR.

## Test Plan 

unit tests

---
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### Type of Change (Check all that apply)

- [ ] protocol change
- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes
implement `get_finalized_bridge_action_maybe` in `EthClient` and
implement simple logic for `BridgeRequestHandler::handle_eth_tx_hash`