fix(ethereum): prevent unhandled L1 rejections from tx monitor loops during shutdown (v5 line, partial) (#24551)

## Flake

`multi-node/slashing/sentinel_status_slash.parallel.test.ts` ("slashes
an attestor that gets stopped after the network is running") flaked on
PR #24507 (unrelated change). CI log:
http://ci.aztec-labs.com/9bb09d2f904e290a

## What actually failed

The test itself **passed**. Immediately after, the node process crashed
with an **unhandled rejection** (`ECONNREFUSED` on anvil after teardown)
— something was still polling L1 after shutdown. Root cause:
`L1TxUtils.monitorTransaction`'s loop calls `getL1Timestamp()` at the
top of its loop, outside the loop's own try/catch, and nothing waited
for in-flight monitor iterations to actually stop during shutdown.

## Scope of this PR (rebased onto `merge-train/spartan-v5`)

This PR was originally written against `next` and touched 4 files. After
rebasing onto `merge-train/spartan-v5`, 2 of those files cherry-picked
cleanly and are included here:

- `yarn-project/ethereum/src/l1_tx_utils/l1_tx_utils.ts` — guards the
loop-top `getL1Timestamp()` call to break quietly when interrupted.
- `yarn-project/sequencer-client/src/publisher/sequencer-publisher.ts` —
adds `.catch` to a bare fire-and-forget `backupDroppedInSim(...)` call.

The other 2 files (`publisher_manager.ts`, `checkpoint_proposal_job.ts`)
have diverged in structure on this branch and needed their own
investigation rather than a blind cherry-pick — that's covered
separately in
[#24560](#24560),
which found `publisher_manager.ts` had the same defect (fixed there) and
`checkpoint_proposal_job.ts` did not (this branch already routes
fire-and-forget L1 requests through a `RequestsTracker` that attaches
its own rejection handler).

No tracked issue exists for this flake; reference only.

---
*Created by
[claudebox](https://claudebox.work/v2/sessions/0959caa9f03f59fa) ·
group: `slackbot`*

Author: AztecBot

yarn-project/ethereum/src/l1_tx_utils/l1_tx_utils.ts

@@ -436,10 +436,23 @@ export class L1TxUtils extends ReadOnlyL1TxUtils {
 
     const initialTxHash = txHashes[0];
     let currentTxHash = txHashes.at(-1)!;
-    let l1Timestamp: number;
+    let l1Timestamp = 0;
 
     while (true) {
-      l1Timestamp = await this.getL1Timestamp();
+      try {
+        l1Timestamp = await this.getL1Timestamp();
+      } catch (err) {
+        // A transient RPC failure here must not abort monitoring with a rejection: callers that
+        // fire this loop in the background would surface it as an unhandled rejection (e.g. when a
+        // test tears down its L1 node while a monitor iteration is in flight). Exit quietly if we
+        // are shutting down, otherwise retry on the next interval.
+        if (this.interrupted) {
+          break;
+        }
+        this.logger.error(`Error fetching L1 timestamp while monitoring tx ${currentTxHash}`, err, { nonce, account });
+        await sleep(gasConfig.checkIntervalMs!);
+        continue;
+      }
 
       try {
         const timePassed = l1Timestamp - state.lastSentAtL1Ts.getTime();

yarn-project/sequencer-client/src/publisher/sequencer-publisher.ts

@@ -469,7 +469,9 @@ export class SequencerPublisher {
 
       if (bundleResult.kind === 'aborted') {
         this.logDroppedInSim(bundleResult.droppedRequests);
-        void this.backupDroppedInSim(bundleResult.droppedRequests);
+        void this.backupDroppedInSim(bundleResult.droppedRequests).catch(err =>
+          this.log.error(`Failed to backup requests dropped in simulation`, err),
+        );
         return undefined;
       }