Integrate conditional partition function UCI solvers for LSFI

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A conditional partition function solver is one that eliminates all but one or a small number of variables, without normalizing, to return, for each value of the non-eliminated variable, the partition function conditioned on that value. UCI has multiple such solvers, VE being the simplest example.

Need to:

• Check with Kalev whether we have these solvers ready to go
• Call these solvers from the solution of the top-level LSFI problem
• Use the results of these solvers to compute LSFI bounds