Add functionality to plot ZNE results with multiple extrapolation techniques

[natestemen]

Motivation

When testing ZNE it can be hard to know which extrapolation technique to use given your data. Visualizing the results from the scaled circuit, as well as what linear/polynomial/exponential fits all look like on the same plot of your data could be very helpful in helping users pick the correct fitting function.

Proposed Solution

from mitiq import zne


folded_circuits = zne.scaled_circuits(circuit, scale_factors, scale_method)

results: list[float] = ...  # circuit execution happens here from the user

# ------------
# NEW FUNCTION
# ------------
zne.visualize_fits(scale_factors, results)  # plots data and various fits

Function signature might need to change, as well as naming.