Improve DAG + Platform Observability info

[lzdanski]

Issue Type

Missing content for an existing feature

Links to Affected Docs

https://www.astronomer.io/docs/astro/dag-metrics

The Issue or Context

We restructured the docs to better separate content intended for Platform Admins vs DAG authors, but by doing so, it obscures the DAG observability features in the sidebar.

Fix or Proposed Change

• [ ] Move the metrics/observability pieces that are DAG-level into a sub-menu about Observability in the Develop DAGs section.
• [ ] Add an algolia rule for search to make sure these topics appear with the appropriate keywords.
• [ ] Include cross linking from pages like View metrics>Deployments (https://www.astronomer.io/docs/astro/deployment-metrics)
• [ ] Add a Platform Observability overview page that better explains the scope and has rerouting options.

Additional Notes

No response

Required Reviewers

MK

[lzdanski]

Related Issue - https://github.com/astronomer/docs/issues/3354