[Post-MVP]: Moving Runs from arbitrary Leaderboard to another

[just-ero]

Say a leaderboard contains an Any% w/ Some Item category that contains an arbitrary number of runs.
Assume now that the game for this leaderboard receives new items and the moderators decide to make the used Item a variable instead, deciding that the items don't obsolete each other.
The runs in that category must now be able to be moved from Any% w/ Some Item to Any% with Some Item as the category's new Item variable.

[TheTedder]

Yeah we should have a whole "admin view" that allows for batch ops like this.