Add flink to root for aggregate publish

[mickjermsurawong-openai]

Summary

• Include Flink in the root so it can be published with same versions together with all other modules

Why / Goal

• Currently to publish flink, we have to run a separate sbt publish doesn't include Flink, and we have to run sbt flink/publish separately
• This is a problem for our internal repo where each release is also versioned with timestamp eg, 0.0.85+openai.20250107.215212; separate flink publish has a separate timestamp and it couldn't find it's online/aggregator dependency of the same timestamp

Test Plan

• Added Unit Tests
• Covered by existing CI
• Integration tested

Checklist

• Documentation update

Reviewers