Rather than ping ponging between codegen and the linker to generate the symbols/atoms
for a local constant and its relocations. We now create all neccesary objects within the linker.

This simplifies the code as we can now simply call `lowerUnnamedConst` from anywhere in codegen,
allowing us to further improve lowering constants into .rodata so we do not have to sacrifice
lowering certain types such as decl_ref's where its type is a slice.