Ability to set custom sort order for albums

[vishnukvmd]

Users might want to sort their albums in a specific order that's convenient to them. We can enable this by letting them long-press and drag and drop in the detailed album view.

https://github.com/ente-io/photos-app/blob/177b1bf3bb42589ccc0a73183a648b3f4023c8d6/lib/ui/collections/album/row_item.dart#L17

This could be a good use case for the reorderables package.

It'd be ideal to preserve this sort order on the server, but it's not a must have for the first cut.