contracts-bedrock: hh task `wait-for-final-deposit`

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 ...
```

packages/contracts-bedrock/tasks/index.ts

@@ -8,3 +8,4 @@ import './solidity'
 import './accounts'
 import './check-l2'
 import './update-dynamic-oracle-config'
+import './wait-for-final-deposit'

packages/contracts-bedrock/tasks/wait-for-final-deposit.ts

+import { task, types } from 'hardhat/config'
+import '@nomiclabs/hardhat-ethers'
+import 'hardhat-deploy'
+import { HardhatRuntimeEnvironment } from 'hardhat/types'
+import { BigNumber } from 'ethers'
+import { sleep, toRpcHexString } from '@eth-optimism/core-utils'
+
+task('wait-for-final-deposit', 'Waits for the final deposit to be ingested')
+  .addParam(
+    'l1RpcUrl',
+    'L1 RPC URL remote node',
+    'http://127.0.0.1:8545',
+    types.string
+  )
+  .addParam(
+    'l2RpcUrl',
+    'L2 RPC URL remote node',
+    'http://127.0.0.1:9545',
+    types.string
+  )
+  .setAction(async (args, hre: HardhatRuntimeEnvironment) => {
+    const l1Provider = new hre.ethers.providers.StaticJsonRpcProvider(
+      args.l1RpcUrl
+    )
+    const l2Provider = new hre.ethers.providers.StaticJsonRpcProvider(
+      args.l2RpcUrl
+    )
+
+    // Handle legacy deployments
+    let Deployment__AddressManager = await hre.deployments.getOrNull(
+      'Lib_AddressManager'
+    )
+    if (!Deployment__AddressManager) {
+      Deployment__AddressManager = await hre.deployments.get('AddressManager')
+    }
+
+    const AddressManager = new hre.ethers.Contract(
+      Deployment__AddressManager.address,
+      Deployment__AddressManager.abi,
+      l1Provider
+    )
+
+    const Deployment__CanonicalTransactionChain = await hre.deployments.get(
+      'CanonicalTransactionChain'
+    )
+    const CanonicalTransactionChain = new hre.ethers.Contract(
+      Deployment__CanonicalTransactionChain.address,
+      Deployment__CanonicalTransactionChain.abi,
+      l1Provider
+    )
+
+    // Wait for DTL_SHUTOFF_BLOCK block to be set in the AddressManager
+    let dtlShutoffBlock = BigNumber.from(0)
+    while (true) {
+      console.log('Waiting for DTL shutoff block to be set...')
+      const val = await AddressManager.getAddress('DTL_SHUTOFF_BLOCK')
+      dtlShutoffBlock = BigNumber.from(val)
+      if (!dtlShutoffBlock.eq(0)) {
+        break
+      }
+      await sleep(3000)
+    }
+
+    console.log(`DTL shutoff block ${dtlShutoffBlock.toString()}`)
+
+    // Now query the number of queue elements in the CTC
+    const queueLength = await CanonicalTransactionChain.getQueueLength()
+    console.log(`Total number of deposits: ${queueLength}`)
+
+    console.log('Searching backwards for final deposit')
+    let height = await l2Provider.getBlockNumber()
+    while (true) {
+      console.log(`Trying block ${height}`)
+      const hex = toRpcHexString(height)
+      const b = await l2Provider.send('eth_getBlockByNumber', [hex, true])
+      const tx = b.transactions[0]
+      if (tx === undefined) {
+        throw new Error(`unable to fetch transaction`)
+      }
+
+      if (tx.queueOrigin === 'l1') {
+        const queueIndex = BigNumber.from(tx.queueIndex).toNumber()
+        if (queueIndex === queueLength) {
+          break
+        }
+        if (queueIndex < queueLength) {
+          console.log()
+          throw new Error(
+            `Missed the final deposit. queueIndex ${queueIndex}, queueLength ${queueLength}`
+          )
+        }
+      }
+      height--
+    }
+
+    console.log('Final deposit has been ingested by l2geth')
+  })