Rewrite host GPU abstraction

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

src/core/shader_cache_version.h

@@ -2,6 +2,6 @@
 // SPDX-License-Identifier: (GPL-3.0 OR CC-BY-NC-ND-4.0)
 
 #pragma once
-#include "types.h"
+#include "common/types.h"
 
-static constexpr u32 SHADER_CACHE_VERSION = 7;
+static constexpr u32 SHADER_CACHE_VERSION = 9;