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