WIP (#1638) - Overwrite previous by_seq docs with new_edits

This works, it should just need a migration which is annoying, it should solve all the constraint error problems

The problem was this code never worked as assumed, but was never being hit, during replication we should expect to miss checkpoints and rewrite previously written documents, but we also do a revsDiff during replication so we never actually ever try to write over old documents, theres a timing issue somewhere in replications in which we can (and we should expect to be able to) which was causing this to show