fix: cache value & cancel tween for instant-set

[tivac]

Fixes #4846

Now when the early-out branch is taken for a duration of 0 it will do two things that were missing in the first implementation:

1. It will cancel any tweens that are in-progress so the value doesn't keep changing after snapping to the specified value.
2. It will cache off the value correctly, so that later tweens use the correct starting point.

Is there a better way to test this within the current suite? The mocha tests don't have access to any browser globals so you can't actually test any tweens and given how broken this was after #4766 the lack of test coverage makes me nervous.

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Tests

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[tivac]

Also fixes #4799, since my bug was actually a dupe of that one.