add initial version of cockroachdb extension

[HarshCasper]

Summary

• Add CockroachDB extension for LocalStack using Docker sidecar pattern
• Run CockroachDB in start-single-node --insecure mode with in-memory store for fast, ephemeral local development
• Route PostgreSQL wire protocol connections through the LocalStack gateway at cockroachdb.localhost.localstack.cloud:4566 via TCP protocol detection
• Include integration tests covering basic connectivity, CRUD operations, and mixed TCP/HTTP traffic co-existence with AWS services
• Add GitHub Actions workflow for CI with lint, build, and integration test steps
• Provide Makefile automation for extension installation, testing, linting, and distribution

[whummer]

Looks great @HarshCasper 🚀 - just checked out the extension locally, and installation and make test are working nicely. 👌

Looks good to go from my side, just added a minor comment which would be great to address before merging.

Btw, just wondering - do we also want to add a simple sample app here (similar to what we did for the other recent extensions), or just get the functionality merged for now? (adding a sample could probably be tackled later 👍 )

[whummer]

note: The custom logic in here should technically no longer be required, after the changes in #130 . Can you try removing this method, and trigger the CI tests again (which should pull in the latest version of localstack-extensions-utils).