[Openscapes] Put dask-gateway workers (and schedulers) on their own nodegroups

[sgibson91]

• fixes Move dask-gateway workers to their own nodegroups on the openscapes cluster #4485

[github-actions]

Merging this PR will trigger the following deployment actions.

Support and Staging deployments

Cloud Provider	Cluster Name	Upgrade Support?	Reason for Support Redeploy	Upgrade Staging?	Reason for Staging Redeploy
aws	openscapes	No		Yes	Following helm chart values files were modified: staging.values.yaml

Production deployments

Cloud Provider	Cluster Name	Hub Name	Reason for Redeploy
aws	openscapes	prod	Following helm chart values files were modified: prod.values.yaml
aws	openscapes	workshop	Following helm chart values files were modified: workshop.values.yaml

[sgibson91]

This needs more investigation as I don't believe the nodeSelectors are working. The dask worker I just span up from the staging hub triggered a scale-up of the dask-workshop nodegroup.

ETA: I was missing a backend key within the dask-gateway config. It's a shame that sort of thing doesn't get picked up by validation.

[github-actions]

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Monitor the deployment of the hubs here 👉 https://github.com/2i2c-org/infrastructure/actions/runs/10160173566