Use history recording and don't do anything permanent

[boatbomber]

Adopts the latest ChangeHistoryService APIs. Our Undo/Redo notification warnings (to prevent accidentally undoing a Rojo patch) still work fine with this new API.

Avoids the permanent Destroy action, uses Remove instead. This closes #914.

[Dekkonot]

I have concerns about memory usage if we make this change, since connections will remain active on Instances now. I know there's not much we can do about it, but I'm still unhappy.

Otherwise, would prefer we not use Remove but looks good to me.

[boatbomber]

not much we can do about it, but I'm still unhappy

Sums up a lot of Rojo work, doesn't it 😭

[kennethloeffler]

Does the problem in the linked issue only occur for changed class names? We destroy instances for normal removals, too

[boatbomber]

Good catch, Ken. Updated all uses of Destroy to be Parent = nil, and updated all the relevant tests to pin this behavior.