[FLINK-35736][tests] Add migration test scripts & CI workflows

[yuxiqian]

This closes FLINK-35736.

Currently, Flink CDC migration tests are limited to per-class unit tests, and it might not cover all migration cases.

Previously I wrote an E2e migration script, thinking this could be useful for RC verification / automated tests. This PR also added it into CI workflows, but I'm not quite sure about it. I'll remove this from GitHub action rules if it's not suitable for CI.

@morazow PTAL