SDL: Migrate to common host interface

It now supports controllers again. But you have to bind them in Qt.

src/duckstation-sdl/duckstation-sdl.vcxproj

@@ -63,6 +63,7 @@
     <ClInclude Include="imgui_impl_sdl.h" />
     <ClInclude Include="opengl_host_display.h" />
     <ClInclude Include="sdl_host_interface.h" />
+    <ClInclude Include="sdl_key_names.h" />
   </ItemGroup>
   <ItemGroup>
     <Manifest Include="duckstation-sdl.manifest" />
@@ -394,4 +395,4 @@
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
-</Project>
+</Project>