Refactor `NDS` and `DSi` to be objects (#1893)

* First crack at refactoring NDS and DSi into objects

- Remove all global/`static` variables in `NDS` and related classes
- Rely more on virtual dispatch when we need to pick methods at runtime
- Pass `NDS&` or `DSi&` to its constituent components where necessary
- Introduce some headers or move some definitions to break `#include` cycles

* Refactor the frontend to accommodate the core's changes

* Move up `SchedList`'s declaration

- Move it to before the components are initialized so the `map`s inside are initialized
- Fields in C++ are initialized in the order they're declared

* Fix a crash when allocating memory

* Fix JIT-free builds

* Fix GDB-free builds

* Fix Linux builds

- Explicitly qualify some member types in NDS, since they share the same name as their classes

* Remove an unnecessary template argument

- This was causing the build to fail on macOS

* Fix ARM and Android builds

* Rename `Constants.h` to `MemConstants.h`

* Add `NDS::IsRunning()`

* Use an `#include` guard instead of `#pragma once`

1 files changed, 1 insertions, 1 deletions

diff --git a/src/GBACart.cpp b/src/GBACart.cpp
index a0c5467..f5e320f 100644
--- a/src/GBACart.cpp
+++ b/src/GBACart.cpp
@@ -850,7 +850,7 @@ void GBACartSlot::LoadAddon(int type) noexcept
 {

     switch (type)

     {

-    case NDS::GBAAddon_RAMExpansion:

+    case GBAAddon_RAMExpansion:

         Cart = std::make_unique<CartRAMExpansion>();

         break;