make the Repository Health Check summary useful for discovering vulnerable components

We wanted to create a way for repo admins to improve the health of their repositories over time. To do this, we made a few improvements to RHC.

1. Show specific components in need of remediation (top 5).
2. Prioritize the list of vulnerable components by severity and impact (downloads in the last 30 days).
3. Include download trends to show how the health of the repository is changing over time