Config: Port remaining Core settings to new config system (partial).

Source/Core/Core/Core.cpp

@@ -636,7 +636,7 @@ static void EmuThread(std::unique_ptr<BootParameters> boot, WindowSystemInfo wsi
   Fifo::Prepare();
 
   // Setup our core, but can't use dynarec if we are compare server
-  if (core_parameter.cpu_core != PowerPC::CPUCore::Interpreter &&
+  if (Config::Get(Config::MAIN_CPU_CORE) != PowerPC::CPUCore::Interpreter &&
       (!core_parameter.bRunCompareServer || core_parameter.bRunCompareClient))
   {
     PowerPC::SetMode(PowerPC::CoreMode::JIT);