WIP: A complete interface to provide more features

[JerryChen97]

The hidden issues in the DMRG for our Kitaev ladders are much more than I expected.
To solve these not-yet-known-why problems, it is necessary to gain full control over the DMRG process, i.e. getting the information of what happened inside the function run_atomic() which served as the most fundamental running function in the past. Here are some examples:

• the total sweeps carried during one run. For quite a few points, the maximum sweeps are reached but the entropy is still not yet converged. To deal with them, we have to specifically set another plan to redo them; therefore, it is necessary to extract the sweep information from the DMRG engine.
• maybe in the future, there will be even more bugs and we need more info from engines. So it is necessary to return all the info.
• the psi_before and the psi_after for calculating the fidelity.

[JerryChen97]

We got a rather good-looking diagram for the entropy.

[JerryChen97]

L = 3