Case list/detail page redesign (revert revert)

Original PR is here: #4553 (with discussion).
This reverts dimagi/commcare-hq#4574 (which reverted #4553).
I haven't looked to see how many app + app builds there are, but I presume it is a big number. I've updated the migration to use `bulk_save`.
Thanks for pointing out that this modifies builds as well. I agree that they should also be migrated.