Improve justified grid to use a row based algorithm

One of the problems of the current justified grid, is that every row has a fixed height. In practice, this means that, if the images in rows have different aspect ratios and dimensions, some of them will be cropped.

Goal is to modify the existing justified grid element to use a row based algorithm, and allow having different rows with different heights.

For now, since the justified grid is only being used in the assets search of the DAM addon, this implementation will rely on picture:info from picture schema to get picture dimensions (works with videos as well).