Allow AREngine to be used independently of ARCodeFile (#2108)

* Make `EmuInstance::cheatFile` use a `unique_ptr`

- Fixes a memory leak, as the cheat file wasn't cleaned up in the destructor

* Split `AREngine` and `ARCodeFile` apart

- Suitable for frontends that have their own way of storing cheats
- Store the cheats in `AREngine` in a `std::vector`
- Apparently cheats are _supposed_ to be executed each frame; I didn't understand this until recently

src/frontend/qt_sdl/EmuInstance.cpp

@@ -686,12 +686,8 @@ void EmuInstance::undoStateLoad()
 
 void EmuInstance::unloadCheats()
 {
-    if (cheatFile)
-    {
-        delete cheatFile;
-        cheatFile = nullptr;
-        nds->AREngine.SetCodeFile(nullptr);
-    }
+    cheatFile = nullptr; // cleaned up by unique_ptr
+    nds->AREngine.Cheats.clear();
 }
 
 void EmuInstance::loadCheats()
@@ -701,9 +697,16 @@ void EmuInstance::loadCheats()
     std::string filename = getAssetPath(false, globalCfg.GetString("CheatFilePath"), ".mch");
 
     // TODO: check for error (malformed cheat file, ...)
-    cheatFile = new ARCodeFile(filename);
+    cheatFile = std::make_unique<ARCodeFile>(filename);
 
-    nds->AREngine.SetCodeFile(cheatsOn ? cheatFile : nullptr);
+    if (cheatsOn)
+    {
+        nds->AREngine.Cheats = cheatFile->GetCodes();
+    }
+    else
+    {
+        nds->AREngine.Cheats.clear();
+    }
 }
 
 std::unique_ptr<ARM9BIOSImage> EmuInstance::loadARM9BIOS() noexcept
@@ -1013,12 +1016,14 @@ void EmuInstance::enableCheats(bool enable)
 {
     cheatsOn = enable;
     if (cheatFile)
-        nds->AREngine.SetCodeFile(cheatsOn ? cheatFile : nullptr);
+        nds->AREngine.Cheats = cheatFile->GetCodes();
+    else
+        nds->AREngine.Cheats.clear();
 }
 
 ARCodeFile* EmuInstance::getCheatFile()
 {
-    return cheatFile;
+    return cheatFile.get();
 }
 
 void EmuInstance::setBatteryLevels()

src/frontend/qt_sdl/EmuInstance.h

@@ -256,7 +256,7 @@ private:
     bool savestateLoaded;
     std::string previousSaveFile;
 
-    melonDS::ARCodeFile* cheatFile;
+    std::unique_ptr<melonDS::ARCodeFile> cheatFile;
     bool cheatsOn;
 
     SDL_AudioDeviceID audioDevice;