Due to various code changes (like #17937, #17879) UI tests are currently failing. This PR aims to fix them again.
Note: I've introduced a new method page.waitForLazyImages(), which removes the loading attribute from all images and then waits for all images to load. Otherwise we can't ensure in some UI tests which images would be loaded or not.
@sgiehl sorry maybe jumped the gun merging there didn't notice @tsteur 's suggestion. Can create a new PR if we want to implement those suggestions also.
@tsteur will check if that works and create a new PR if so