feat: Support Flink 2.3

[james-kan-shopify]

Summary

Flink 2.3 has been released for a while. The current connector officially supports up to 2.1. Combined changes from Flink 2.2 and Flink 2.3 don't significantly affect connectors significantly based on release notes. The connector should be able to jump from 2.1 to 2.3.

Resources

• Flink 2.3 Release notes: https://nightlies.apache.org/flink/flink-docs-stable/release-notes/flink-2.3/
• Flink 2.2 Release notes: https://nightlies.apache.org/flink/flink-docs-stable/release-notes/flink-2.2/