Make IOpenGLContext.HasContext context dependent (#6290)

This makes IOpenGLContext.HasContext not static and be implementable.

By doing this, we can support more than WGL and WGL.

This also allows the SDL2 headless version to run under Wayland.

Signed-off-by: Mary <mary@mary.zone>

src/Ryujinx.Headless.SDL2/OpenGL/OpenGLWindow.cs

@@ -96,6 +96,8 @@ namespace Ryujinx.Headless.SDL2.OpenGL
                 }
             }
 
+            public bool HasContext() => SDL_GL_GetCurrentContext() != IntPtr.Zero;
+
             public void Dispose()
             {
                 SDL_GL_DeleteContext(_context);