Enable non-Hermitian MR-LDSRG(2)

[brianz98]

Description

Enable non-Hermitian MR-LDSRG(2), for both spin-integrated and spin-adapted versions.

Checklist

• Added/updated tests of new features and included a reference output.ref file
• Enable non-Hermitian for SI code (this is just by removing a previous restriction)
• Enable non-Hermitian for SA code
• Enable non-Hermitian for SO code
• Documented new features in the manual
• Ready to go!

[fevangelista]

Can we get @lcyyork's blessing on this PR?

[brianz98]

Only DMRG tests are failing (need further investigation but unrelated to this PR). New tests all passing.

[brianz98]

Tests passing, ready to go. Non-Hermitian is enabled for all but three cases:

• Sequential transformation
• Quadratic commutator approximation
• Reference relaxation

[brianz98]

DMRG tests are now temporarily disabled due to github runners not playing well with them

[lcyyork]

Sorry for being late in the game. I would check if the results are correct or not by keeping the intermediate hamiltonian hermitian without adding it to the final DSRG hamiltonian.