perf: optimize get_unsealed_l1_batch_inner (#3491)

## What ❔

optimize get_unsealed_l1_batch_inner

## Why ❔

<!-- Why are these changes done? What goal do they contribute to? What
are the principles behind them? -->
<!-- Example: PR templates ensure PR reviewers, observers, and future
iterators are in context about the evolution of repos. -->

## Checklist

<!-- Check your PR fulfills the following items. -->
<!-- For draft PRs check the boxes as you complete them. -->

- [ ] PR title corresponds to the body of PR (we generate changelog
entries from PRs).
- [ ] Tests for the changes have been added / updated.
- [ ] Documentation comments have been added / updated.
- [ ] Code has been formatted via `zkstack dev fmt` and `zkstack dev
lint`.

core/lib/dal/src/blocks_dal.rs

@@ -835,10 +835,21 @@ impl BlocksDal<'_, '_> {
                 l1_gas_price,
                 l2_fair_gas_price,
                 fair_pubdata_price
-            FROM
-                l1_batches
-            WHERE
-                NOT is_sealed
+            FROM (
+                SELECT
+                    number,
+                    timestamp,
+                    protocol_version,
+                    fee_address,
+                    l1_gas_price,
+                    l2_fair_gas_price,
+                    fair_pubdata_price,
+                    is_sealed
+                FROM l1_batches
+                ORDER BY number DESC
+                LIMIT 1
+            ) AS u
+            WHERE NOT is_sealed
             "#,
         )
         .instrument("get_unsealed_l1_batch")