Implement a termination criterion for qiskit_algorithm's SPSA

[dleidreiter]

SPSA is a promising noise resistant classical optimizer for VQA routines. It is implemented in qiskit_algorithms and seemlessly usable within this implementation of EVQE. Yet unlike other classical optimizers in qiskit_algorithms, SPSA does not offer a stability based termination criterion, only a callback so the user can decide themselves whether to terminate. To prevent running needlessly many SPSA iterations in EVQE, a termination criterion should be offered for the SPSA optimizer.