Add logging capabilities

[wavefunction91]

GauXC is a complicated project with many interrelated components. It would drastically improve debugging processes to include a logger to facilitate program introspection. This would also enable GauXC to notify users of program state / warnings in a matter that can be runtime configurable (i.e. not always blasting stdout).

spdlog comes to mind as it's been used elsewhere throughout the NWChemEx stack. Logging should also be made optional as to avoid the requirement of additional dependencies

[susilehtola]

This discussion is also of some interest for https://github.com/susilehtola/OpenOrbitalOptimizer, even though that project is quite a bit more user facing