Make the NDS teardown more robust (#1798)

* Make cleanup a little more robust to mitigate undefined behavior

- Add some null checks before cleaning up the GPU3D renderer
- Make sure that all deleted objects are null
- Move cleanup logic out of an assert call
- Note that deleting a null pointer is a no-op, so there's no need to check for null beforehand
- Use RAII for GLCompositor instead of Init/DeInit methods

* Replace a DeInit call that I missed

* Make ARMJIT_Memory less likely to generate errors

- Set FastMem7/9Start to nullptr at the end
- Only close and unmap the file if it's initialized

* Make Renderer3D manage its resources with RAII

* Don't try to deallocate frontend resources that aren't loaded

* Make ARMJIT_Memory::DeInit more robust on the Switch

* Reset MemoryFile on Windows to INVALID_HANDLE_VALUE, not nullptr

- There is a difference

* Don't explicitly store a Valid state in GLCompositor or the 3D renderers

- Instead, create them with static methods while making the actual constructors private

* Make initialization of OpenGL resources fail if OpenGL isn't loaded

* assert that OpenGL is loaded instead of returning failure

src/GPU3D.h

@@ -137,14 +137,11 @@ void Write32(u32 addr, u32 val);
 class Renderer3D
 {
 public:
-    Renderer3D(bool Accelerated);
-    virtual ~Renderer3D() {};
+    virtual ~Renderer3D() = default;
 
     Renderer3D(const Renderer3D&) = delete;
     Renderer3D& operator=(const Renderer3D&) = delete;
 
-    virtual bool Init() = 0;
-    virtual void DeInit() = 0;
     virtual void Reset() = 0;
 
     // This "Accelerated" flag currently communicates if the framebuffer should
@@ -159,6 +156,8 @@ public:
     virtual void RenderFrame() = 0;
     virtual void RestartFrame() {};
     virtual u32* GetLine(int line) = 0;
+protected:
+    Renderer3D(bool Accelerated);
 };
 
 extern int Renderer;