fix(l2): remove empty account diffs from payload builder's blob size estimation

[xqft]

Motivation

The payload builder estimates the state diff encoded size before adding another transaction to the block to make sure that we can fit it in a blob, and a batch can be committed with that single block.

When I executed load tests on the L2 the batch size metric reported 0, so I initially suspected that the estimation was wrong (smaller than the real state diff size) and I investigated the implementation but found that the batch size metric was wrong instead, and the estimation was correct*.

*Nevertheless I found that sometimes get_account_diffs_in_tx() returns empty account diffs (I think because of accounts in the callframe's original state that didn't participate in that transaction) and they get accounted when estimating the state diff size, making the estimation larger than the true value.

Description

• prevent get_account_diffs_in_tx() to retrieve empty account diffs
• add an internal error in the case that the sequencer can't make a single block batch because of blob size, instead of getting stuck silently.

Closes #issue_number

[github-actions]

Lines of code report

Total lines added: 7
Total lines removed: 0
Total lines changed: 7

Detailed view

+--------------------------------------------------------------+-------+------+
| File                                                         | Lines | Diff |
+--------------------------------------------------------------+-------+------+
| ethrex/crates/l2/sequencer/block_producer/payload_builder.rs | 344   | +2   |
+--------------------------------------------------------------+-------+------+
| ethrex/crates/l2/sequencer/l1_committer.rs                   | 539   | +5   |
+--------------------------------------------------------------+-------+------+