Switch to Kueue service backend

[cortadocodes]

Summary

This release switches to running Twined services on Kubernetes + Kueue. This brings the following features:

• Queue questions so they're not just dropped if the service backend is overwhelmed
• Run questions that take any amount of time (specifically opening us up to runs > 1 hour)
• Request arbitrary compute resources per question (CPU, memory, storage etc.)
• Stop extraneous question reruns by allowing us to control when we acknowledge question events
• Monitor running questions individually
• Make it easier to run questions on providers other than Google in the future (i.e. on any Kubernetes cluster)

Contents (#723)

IMPORTANT: There are breaking changes.

New features

• Add Kubernetes/Kueue service backend #709 (see PR for list of breaking changes)
• Authenticate requests to service registries

Enhancements

• Add allow_not_found option to ServiceConfiguration.from_file
• Add default event store ID to get_events
• Increase default maximum heartbeat interval to 360s

Refactoring

• Factor out attributes into EventAttributes class #721

Dependencies

• Remove gunicorn and Flask dependencies

Operations

• Replace Terraform configuration with new terraform-octue-twined-core module

Testing

• Move deployment test to octue/example-service-kueue repository