Adds a hh task that can be used as part of the automation
to wait for the final deposit to be ingested by `l2geth`.
It first waits until the dtl shutoff block is set in the
address manager and then it works backwards from the tip
of the sequencer to find the final deposit

To run the script:

```bash
$ npx hardhat wait-for-final-deposit \
    --l2-rpc-url https://mainnet.optimism.io \
    --network mainnet \
    --l1-rpc-url ...
```