Motivation
After T250144 is done, the getting of real thumbnail should be implemented.
The most appropriate is PageImages but might other options are possible. So it should be defined later.
Expected Results
- Hook 'SearchResultProvideThumbnails' introduced in T250144, should be implemented
- The hook should return thumbnails for a given list of pages (or null if no thumb for the page)
- Tests should cover changes properly
- Thumbnail should be 200x200 px (changed from 512x512)
- Thumbnail's size should be optional.