Include schema info on the diagnostic view and download

[nwmac]

Summary

Fixes #11231

Occurred changes and/or fixed issues

This PR updates the diagnostic page to fetch schema info for the clusters in addition to counts.

It then includes that in the report on screen and the download json.

Areas or cases that should be tested

Test the diagnostic page renders and that the download still works.

Screenshot/Video

Diagnostic page now shows schema count for each cluster and shows the custom schemas for a given cluster:

Checklist

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• The PR has been self reviewed
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• The PR has automated tests or clear instructions for manual tests and the linked issue has appropriate QA labels, or tests are not needed
• The PR has reviewed with UX and tested in light and dark mode, or there are no UX changes

[aalves08]

Gave it a test and works just fine. Could generate the response times and download the json. LGTM!