Find a way to use the centerless 3x3x3 definition for SolvingBasedScrambleFinder?

[lgarron]

Right now the scrambles for different events use the same SolvingBasedSrambleFinder. This allows generating scrambles across events more quickly, but is wasteful for 3×3×3 scrambles that don't need centers. Perhaps there's a way to get the best of both worlds.

It's possible that the impact of perf is low enough that keeping centers in the definition is worth it, though. This also makes it easier to perform operations on patterns across events.