FD Debug Util

Make a utility class to handle finite-difference debugger routines currently housed in main.cpp.

I'd like to be able to run FD debugging on different methods without having to modify and recompile the code.

Might also throw some stuff into the test suite!

• Can I figure out an "only run these tests sometimes" option, so as to not bog down the CI pipelines too much?

Code design plan:

• Input: a dynamically casted Method_ pointer
• The Guts:
  • Set up a if/else section in main.cpp to make calls to certain debugger routines based on Method_ type
  • A debugger class in yucca/util that has one function per each FD debug routine implemented
• Output: some error numbers that YuccaTest can work with

Coding Checklist:

• Set up debugger functions in a util header file
  • Fock matrix for SCF debugger
  • Fock matrix for restricted ResHF debugger
  • Fock matrix for unrestricted ResHF debugger
  • DF gradients for SCF debugger
• Review debugging access functions to ensure everything is properly set-up
• Move uResHF and rResHF debugger functions to class header files (delete the util/debug.cpp stuff)