Now that we have most of core free of shadowing, we can enable the
warning as an error to catch anything that may be remaining and also
eliminate this class of logic bug entirely.
When zero byte files are present, the key (offset) for that file is identical to the file right after. A std::map isn't able to fit key-value pairs with identical keys (offsets), therefore, the solution is to use std::multimap which permits multiple entries with the same key.
This most prominently fixes Pokemon Sword and Shield weather with any RomFS mod applied.
Given these are only added to the class to allow those functions to
access the private constructor, it's a better approach to just make them
static functions in the interface, to make the dependency explicit.
This converts it into a regular constructor parameter. There's no need
to make this a template parameter on the class when it functions
perfectly well as a constructor argument.
This also reduces the amount of code bloat produced by the compiler, as
it doesn't need to generate the same code for multiple different
instantiations of the same class type, but with a different fill value.
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.
