Make the FSM_STATE work better with optional loggins set by a define and standardize on using enum class by default.

game_engine.cpp

@@ -6,6 +6,8 @@
 #include "game_engine.hpp"
 #include <cassert>
 
+#define FSM_DEBUG 1
+
 const auto ERROR = fmt::emphasis::bold | fg(fmt::color::red);
 
 using namespace fmt;