Refactor: extract highest energy bound with tsdrg variant

[tanlin2013]

Reverse the spectrum with an overall constant -1 doesn't seem to help for extracting the highest energy, results didn't converge to a stable region, although the reason requires further thoughts.

In turn, it's better to use a tsdrg variant, which reserve highest energies as each fusing step, and so there is no need to reverse the Hamiltonian with any overall const. We can just feed in the MPO into this tsdrg variant.

Reference

tanlin2013/tnpy@8c36865