fix: mimic BSS timestamp bug fix from #2093

See https://github.com/ethereum-optimism/optimism/pull/2093 for more
details.

.changeset/many-seals-argue.md

+---
+'@eth-optimism/batch-submitter-service': patch
+---
+
+Adds a fix for the BSS to account for the new timestamp logic in L2Geth

go/batch-submitter/drivers/sequencer/batch.go

@@ -91,11 +91,10 @@ func GenSequencerBatchParams(
 
 	// Iterate over the batch elements, grouping the elements according to
 	// the following critera:
-	//  - All sequencer txs in the same group must have the same timestamp
-	//     and block number.
+	//  - All txs in the same group must have the same timestamp.
+	//  - All sequencer txs in the same group must have the same block number.
 	//  - If sequencer txs exist in a group, they must come before all
 	//     queued txs.
-	//  - A group should never split consecutive queued txs.
 	//
 	// Assuming the block and timestamp criteria for sequencer txs are
 	// respected within each group, the following are examples of groupings:
@@ -110,17 +109,18 @@ func GenSequencerBatchParams(
 		// To enforce the above groupings, the following condition is
 		// used to determine when to create a new batch:
 		//  - On the first pass, or
-		//  - Whenever a sequecer tx is observed, and:
+		//  - The preceding tx has a different timestamp, or
+		//  - Whenever a sequencer tx is observed, and:
 		//    - The preceding tx was a queued tx, or
-		//    - The preceding sequencer tx has a different
-		//       block number/timestamp.
-		// Note that a sequencer tx is required to create a new group,
-		// so a queued tx may ONLY exist as the first element in a group
-		// if it is the very first element.
+		//    - The preceding sequencer tx has a different block number.
+		// Note that a sequencer tx is usually required to create a new group,
+		// so a queued tx may ONLY exist as the first element in a group if it
+		// is the very first element or it has a different timestamp from the
+		// preceding tx.
 		needsNewGroupOnSequencerTx := !lastBlockIsSequencerTx ||
-			el.Timestamp != lastTimestamp ||
 			el.BlockNumber != lastBlockNumber
 		if len(groupedBlocks) == 0 ||
+			el.Timestamp != lastTimestamp ||
 			(el.IsSequencerTx() && needsNewGroupOnSequencerTx) {
 
 			groupedBlocks = append(groupedBlocks, groupedBlock{})