Platform: Run automated E2E tests for all code merges to main branch

This issue warrants we start developing & running E2E tests for all merges into main. Given our current deployment surface, we're getting to a point wherein releasing new changes and/or features would be better of tested more comprehensively.

From an implementation/scalability perspective, we should reuse once-provisioned infrastructure (NATS, ClickHouse, Remote Storage) e.g. inside the pre-staging environment and only need to install DIP components via the helm-chart for a given tag/SHA. We can "namespace" all resources to have necessary isolation across the different runs. We also discussed this capability within #7.