PlanetScale migrates open source Vitess test suite from Python to Go

Migrated the Vitess integration test suite from Python to Go, reducing development and debugging time, removing dependencies, and aligning with Python 2.7 end-of-life. Developed a Go test framework to programmatically interact with Vitess clusters, supporting parallel tests and non-conflicting working directories. Switched the CI pipeline from Travis CI to GitHub Actions to leverage larger compute instances and overcome concurrency limits, enabling more parallel test shards and faster feedback.