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`

src/ARMInterpreter_ALU.cpp

@@ -18,6 +18,7 @@
 
 #include <stdio.h>
 #include "ARM.h"
+#include "NDS.h"
 
 namespace melonDS::ARMInterpreter
 {
@@ -692,7 +693,7 @@ void A_MOV_REG_LSL_IMM_DBG(ARM* cpu)
         // but since they serve no purpose ATTOW, we can skip them
         u32 addr = cpu->R[15] + 4; // Skip 2nd ID and flags
         // TODO: Pass flags to NocashPrint
-        NDS::NocashPrint(cpu->Num, addr);
+        cpu->NDS.NocashPrint(cpu->Num, addr);
     }
 }
 
@@ -1561,7 +1562,7 @@ void T_MOV_HIREG(ARM* cpu)
         // but since they serve no purpose ATTOW, we can skip them
         u32 addr = cpu->R[15] + 4; // Skip 2nd ID and flags
         // TODO: Pass flags to NocashPrint
-        NDS::NocashPrint(cpu->Num, addr);
+        cpu->NDS.NocashPrint(cpu->Num, addr);
     }
 }