This is in attempt to make compile times better, as the old json library
was quite slow to compile due to many template instantiations and such a
large header.
macOS tests have shown build times from 610s to ~390s, about a 1.5x
speedup
Co-authored-by: camila314 <47485054+camila314@users.noreply.github.com>
this removes submodules and external libraries in the code in favor of
importing them as CPM packages. CPM_SOURCE_CACHE is recommended as
codegen has to readd two of the same dependencies
