Adaptive QRAC

[garrison]

What is the expected enhancement?

Let n represent the value of max_vars_per_qubit. Let's further assume that n is not 1, i.e. it is either 2 or 3. Depending on the variables-to-qubits assignment, it is possible that some qubits will have fewer than n decision variables assigned. However, at the moment, such qubits will still be encoded as an (n,1,p) QRAC. Ideally, the encoding on each qubit will be "adaptive," such that it uses an (m_i,1,p) QRAC, where m_i is the precise number of decision variables assigned to that qubit.

This is not difficult to fix, but we need to fix #7 first (update: done!); otherwise, magic rounding would no longer work generally.