Precalculate trending projects

## What does this MR do?

This MR changes the trending projects code so that data is precalculated, removing the need for any complex caching mechanisms. 

## Why was this MR needed?

Caching of trending data didn't work properly, still leading to queries. Using caching in general would be very hard due to users being able to apply custom filters to the list of trending projects.

See merge request !6749