[Artworks] Store actual artwork brick aspect ratio after layout.

[alloy]

We currently only use the image’s aspect ratio to do masonry layout, but sometimes the metadata below the image is shorter and sometimes taller, this may be the reason why at some point the layout can skew to either the left or the right side. Additionally we default to an aspect ratio of 1:1 when it’s missing from the payload.

We should probably register for the onLayout callback of each artwork brick and update the aspect ratio for the full brick after layout. This shouldn’t lead to already laid-out artworks to re-layout, but it will correct the layout of new artworks being paginated in, as the total aspect ratio of the columns will be correct.