Lemmy Server Performance, two birds with one stone, mass deletes of content: Account Delete, Community Delete, User Ban - moving these operations to a linear queue and add undo support / grace period

A general description of the proposed change and reasoning behind it is on GitHub: https://github.com/LemmyNet/lemmy/issues/3697

Linear execution of these massive changes to votes/comments/posts with concurrency awareness. Also adds a layer of social awareness, the impact on a community when a bunch of content is black-holed.

An entire site federation delete / dead server - also would fall under this umbrella of mass data change with a potential for new content ownership/etc.