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_Soft.cpp

@@ -71,13 +71,8 @@ void SoftRenderer::SetupRenderThread()
 }
 
 
-SoftRenderer::SoftRenderer()
+SoftRenderer::SoftRenderer() noexcept
     : Renderer3D(false)
-{
-
-}
-
-bool SoftRenderer::Init()
 {
     Sema_RenderStart = Platform::Semaphore_Create();
     Sema_RenderDone = Platform::Semaphore_Create();
@@ -86,11 +81,9 @@ bool SoftRenderer::Init()
     Threaded = false;
     RenderThreadRunning = false;
     RenderThreadRendering = false;
-
-    return true;
 }
 
-void SoftRenderer::DeInit()
+SoftRenderer::~SoftRenderer()
 {
     StopRenderThread();