SPSA optimization example

[refraction-ray]

Task description

Example demonstrating VQE optimization using SPSA via https://github.com/andim/noisyopt package

Implementation

add an scripts in examples or an jupyter notebook in doc/source/tutorials, actually slight change on https://github.com/tencent-quantum-lab/tensorcircuit/blob/master/examples/vqe_shot_noise.py

recommend to also include benchmark on the optimization performance comparison with other optimizers

Requirements

Difficulty: ★★