Rewrite host GPU abstraction

- Don't have to repeat the same thing for 4 renderers.
 - Add native Metal renderer.

src/duckstation-nogui/duckstation-nogui.vcxproj.filters

@@ -3,7 +3,6 @@
   <ItemGroup>
     <ClCompile Include="nogui_host.cpp" />
     <ClCompile Include="win32_nogui_platform.cpp" />
-    <ClCompile Include="vty_nogui_platform.cpp" />
     <ClCompile Include="wayland_nogui_platform.cpp" />
     <ClCompile Include="x11_nogui_platform.cpp" />
   </ItemGroup>
@@ -11,8 +10,6 @@
     <ClInclude Include="resource.h" />
     <ClInclude Include="nogui_host.h" />
     <ClInclude Include="win32_nogui_platform.h" />
-    <ClInclude Include="vty_nogui_platform.h" />
-    <ClInclude Include="vty_key_names.h" />
     <ClInclude Include="nogui_platform.h" />
     <ClInclude Include="wayland_nogui_platform.h" />
     <ClInclude Include="x11_nogui_platform.h" />