Symbol export

[yhmtsai]

This PR tries to export the symbols manually.
It is passed on enabled ref/omp from my side, but it was mostly to enable the symbol when the compilation report unresolved symbol.
Thus, there will still be another round to ensure having the same logic on all of them.
MSVC has different logic on export and import than GCC/CLANG.
Also, Ginkgo has complex setting especially in core. For example, OmpExecutor has different copy is implemented in different backends.

In most cases, instantiation follows the visibility when declaring export in the template declaration in GCC/CLANG. Some needs to export them in instantiation explicitly. In MSVC, we always need to export them in instantiation/definition, but we still need to have them in declaration for importing.
Thus, I go for export/import in declaration and definition in both cases.

vtable symbol sometimes needs explicitly exported in GCC/CLANG but no need in MSVC.
MSVC does not like export the class, which uses std member.
If exporting the entire class, the class inheriting from the base class requires the base class fully imported. This also makes some difficulty in the current ginkgo structure.
In short, we only have export class for GCC/CLANG, but still export function on both side.

I will take the necessary part from GenerateExportHeader with the optional export on class macro.