fix(contracts): check actual number of transactions in each chunk

[zimpha]

Purpose or design rationale of this PR

This PR check the actual number of transactions in each chunk instead of only L2 transactions, which is consistent with batch proposer and zkevm circuits.

PR title

Your PR title must follow conventional commits (as we are doing squash merge for each PR), so it must start with one of the following types:

• fix: A bug fix

Deployment tag versioning

Has tag in common/version.go been updated?

• No, this PR doesn't involve a new deployment, git tag, docker image tag
• Yes

Breaking change label

Does this PR have the breaking-change label?

• No, this PR is not a breaking change
• Yes

[github-actions]

LCOV of commit c9effa3 during Contracts #1340

Summary coverage rate:
  lines......: 52.6% (992 of 1885 lines)
  functions..: 67.3% (222 of 330 functions)
  branches...: no data found

Files changed coverage rate: n/a