Chore: remove convert to fanci

[kzsigmond]

This pull request removes the obsolete convert_to_fanci wavefunction utility. This function previously set up the class GeneratedFanCI, which is equivalent to the ProjectedSchrodingerPyCI and ProjectedSchrodingerFanCI classes. All of these three classes inherit from a version of the Fanci class that lives in PyCI now. They set up the compute overlap and compute overlap deriv methods, and have their own optimize methods too.

In order to reduce the maintenance burden, the GeneratedFanCI class, which lives inside convert_to_fanci has been removed. convert_to_fanci initialized the GeneratedFanCI class with the input parameters the user passes to the function. Since it only passes the parameters and does not do any data transformation or manipulation, convert_to_fanci has also been removed from the code base.

Test updates:

• wfn utils has now 100% coverage
• the fanpt tests have a fixme comment in them to signify that convert_to_fanci needs to be updated to the new interface. The import for convert_to_fanci has been removed. Since the tests are skipped, it is not an issue that we do not import it.

Examples:

• I added a comment to the script regarding the removal of convert_to_fanci