health api: add `GET /_health_report` endpoint

[yaauie]

Release notes

[rn: skip] (notes to be added on PR for merging feature branch

What does this PR do?

Adds GET /_health_report API endpoint

Why is it important/What is the impact to the user?

Part of the delivery of #16056

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have commented my code, particularly in hard-to-understand areas
• ~~[ ] I have made corresponding changes to the documentation~~
• ~~[ ] I have made corresponding change to the default configuration files (and/or docker env variables)~~
• [ ] I have added tests that prove my fix is effective or that my feature works