Add examples benchmarking different contractor settings provided by cotengra

[king-p3nguin]

Resolve #212

(I am contributing to this project as a unitaryHACK participant)

[refraction-ray]

thanks for the nice contribution. merged with some small tweaks:

1. increase the max_time to 60
2. comment most of the options by default
3. use reuse=False in expectation calculation to directly compute the tensor network for the observable

[refraction-ray]

I find that jitting the function here speeds up the path-finding time

this part still requires further investigation in the future as the path finding stage seems to be irrelevant from jitting things as they are implemented outside the ML backend.