[ENHANCEMENT] Generalize the `"Rn"` operator to `"Qudit"`/high spin

[mtfishman]

Generalize the "Rn" operator to "Qudit" by exponentiating the high-spin operators (see https://docs.quantum.ibm.com/api/qiskit/qiskit.circuit.library.UGate, https://en.wikipedia.org/wiki/Spin_(physics)#Rotations, https://en.wikipedia.org/wiki/Pauli_matrices#Exponential_of_a_Pauli_vector).