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_recompiler_thunks.h

@@ -13,6 +13,7 @@ namespace Recompiler::Thunks {
 // TODO: Abuse carry flag or something else for exception
 //////////////////////////////////////////////////////////////////////////
 bool InterpretInstruction();
+bool InterpretInstructionPGXP();
 
 // Memory access functions for the JIT - MSB is set on exception.
 u64 ReadMemoryByte(u32 address);