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.filters

@@ -12,6 +12,7 @@
     <ClInclude Include="sdl_host_interface.h" />
     <ClInclude Include="d3d11_host_display.h" />
     <ClInclude Include="imgui_impl_sdl.h" />
+    <ClInclude Include="sdl_key_names.h" />
   </ItemGroup>
   <ItemGroup>
     <Manifest Include="duckstation-sdl.manifest" />