fix(fd): make sure fd doesn't sync beyond tip (#2793)

Fixes a bug where the FD would try to get blocks beyond the local tip,
triggering an error in L2Geth.
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

.changeset/silly-hornets-grab.md

+---
+'@eth-optimism/fault-detector': patch
+---
+
+Fix bug where FD would try to sync beyond local tip

packages/fault-detector/src/service.ts

@@ -135,6 +135,16 @@ export class FaultDetector extends BaseServiceV2<Options, Metrics, State> {
 
     const batchStart = event.args._prevTotalElements.toNumber() + 1
     const batchSize = event.args._batchSize.toNumber()
+    const batchEnd = batchStart + batchSize
+
+    const latestBlock = await this.options.l2RpcProvider.getBlockNumber()
+    if (latestBlock < batchEnd) {
+      this.logger.info(`node is behind, waiting for sync`, {
+        batchEnd,
+        latestBlock,
+      })
+      return
+    }
 
     // `getBlockRange` has a limit of 1000 blocks, so we have to break this request out into
     // multiple requests of maximum 1000 blocks in the case that batchSize > 1000.