CPU: Implement PGXP CPU Mode

This is *very* slow. You don't want to enable it if you don't need it.
It is also incompatible with the recompiler and will disable it if the
option is enabled.

src/core/cpu_code_cache.h

@@ -96,6 +96,7 @@ void SetUseRecompiler(bool enable);
 /// Invalidates all blocks which are in the range of the specified code page.
 void InvalidateBlocksWithPageIndex(u32 page_index);
 
+template<PGXPMode pgxp_mode>
 void InterpretCachedBlock(const CodeBlock& block);
 void InterpretUncachedBlock();