helm: Add GEM federation-frontend resources

[dimitarvdimitrov]

What this PR does

This PR adds the federation-frontend resources to the Helm chart. The goal is to have the federation-frontend deployed on its own.

• Adds resources for the federation-frontend
  • Service
  • Deployment
  • PodDisruptionBudget
  • ServiceMonitor (if meta-monitoring is enabled)
• Adds an offline test with the current way of deploying a stand-alone federation-frontend:
  • GEM gateway (to allow deploying the federation-frontend in an existing cluster)
  • admin-api, so that the GEM license is set up in case this is a standalone GEM cluster too (albeit with a single query component)
  • minio to allow local testing for the admin-api
  • most other components are scaled to 0 replicas or disabled. My plan is to later add enabled toggles for all components so there are no unrelated components deployed

I've tested this locally with the test-enterprise-federation-frontend-values.yaml (+ license) by deploying a Mimir cluster and pointing the federation-frontend to it

Which issue(s) this PR fixes or relates to

related to #9672

Checklist

• Tests updated.
• Documentation added.
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX].
• about-versioning.md updated with experimental features.

[narqo]

🔥 Looks good to me.

(Thinking out loud) I'd maybe added a new validation in validation.yaml, that asserts federation_frontend=true && enterprise=true. But we seem to not do that generally, and I think it won't be too much of an obscure issue for a user, who might set randomly.