Added proof-of-concept implementations for ChangeSetBuilder classes

[JakenVeina]

This idea was brought up once or twice, at least during our last voice call, and I've found actual use for this in a personal project, so I figured I'd toss them in. Not really married to any of the functionality here, we can drop them later if they don't end up being terribly useful.

[github-actions[bot]]

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