Several classes have a lot of non-trivial members within them, or don't
but likely should have the destructor defaulted in the cpp file for
future-proofing/being more friendly to forward declarations.
Leaving the destructor unspecified allows the compiler to inline the
destruction code all over the place, which is generally undesirable from
a code bloat perspective.
Avoids the need to rebuild whatever includes the romfs factory header if
the loader header ever changes. We also don't need to include the main
core header. We can instead include the headers we specifically need.
