Fix bug in Davidson-Liu and upgrade tests to use Forte's MCSCF code

[fevangelista]

Description

This PR started with the goal of fixing a small issue with the python test cases. The problem was easily fixed by zeroing the sigma vectors upon collapse of the Davidson-Liu solutions. However, due to changes in psi4 many test cases that use the MCSCF module in psi4 failed to pass. This was a good motivation to move all tests to use Forte's MCSCF_TWO_STEP code.

User Notes

• Fixed bug in DL that affected some python tests
• Cleaned up checks for orthonormality of DL solutions
• Add check for symmetry of DL projected Hamiltonian
• Changed all tests that use mcscf to use mcscf_two_step
• Checks that string options match allowed values (when an allowed list is provided)
• Finite difference optimization is broken because of issues with how options are handled across psi4/forte (see Fix finite difference #306)
• Some reference values have changed, especially for tests: mrdsrg-ldsrg2-qc-df-2
• Fixed bug in SigmaVectorSparse class due to race condition

Checklist

• Added/updated tests of new features and included a reference output.ref file
• Removed comments in code and input files
• Documented source code
• Checked for redundant headers
• Checked for consistency in the formatting of the output file
• Documented new features in the manual
• Ready to go!