fix(ingest/partition-executor): Fix deadlock by recomputing ready items

[asikowitz]

See https://acryldata.slack.com/archives/C07TL7BRYMQ/p1731533452308859 for deadlock discussion

Checklist

• [ ] The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• [ ] Links to related issues (if applicable)
• [ ] Tests for the changes have been added/updated (if applicable)
• [ ] Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• [ ] For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub