Fix images order on search results

It fixes regression that was introduced by https://github.com/spree/spree/pull/5352. When association is loaded using eager_load, it doesn't respect images ordering. Maybe its rails bug, and it should be fixed there or maybe its just better to use includes as its much better documented. Attached test is passing now, and failing on earlier version. 

To reproduce bug:
- Add new product with few photos
- Save
- Change photos order, move some photo to first position.

Photos will be returned in some default order, probably in the same order they were added.