GPU: Implement FIFO and timings

This will cause a slight performance loss. I've left some knobs in which
can be tweaked to mitigate this, but the goal is to be compatible with
all games which require them.

src/core/save_state_version.h

@@ -2,4 +2,4 @@
 #include "types.h"
 
 static constexpr u32 SAVE_STATE_MAGIC = 0x43435544;
-static constexpr u32 SAVE_STATE_VERSION = 22;
+static constexpr u32 SAVE_STATE_VERSION = 23;