Web Analytics: Aggregate and page-specific web vitals info

[robbie-c]

Feature request

Describe the solution you'd like

We already capture web vitals information, but it's only used in replay

(LCP is also in web analytics but behind a feature flag, and I wasn't really happy with how the feature turned out).

Instead of just showing the LCP score in web analytics, we could show the general web vitals health level of the site, and if clicked, could take to a dedicated page that shows which issues / pages need to be looked at. We have this data already, we'd just need to query it and build the UI.

We could also show session recording of the problems pages, if this works well (I'm not sure we'd get a good recording of a slow initial page load, but it could demonstrate other issues)

Describe alternatives you've considered

This could live more in session replay instead, and be part of the session replay summaries work.