[Cleanup] Gender constants cleanup (#3817)

* [Cleanup] Gender constants cleanup

# Notes
- Convert to a `Gender` namespace using `constexpr`.
- Cleanup spots where we were using magic numbers for gender values.

* Cleanup

zone/bot.cpp

@@ -281,10 +281,10 @@ Bot::Bot(
 				case SE_IllusionCopy:
 				case SE_Illusion: {
 					if (spell.base_value[x1] == -1) {
-						if (gender == FEMALE) {
-							gender = MALE;
-						} else if (gender == MALE) {
-							gender = FEMALE;
+						if (gender == Gender::Female) {
+							gender = Gender::Male;
+						} else if (gender == Gender::Male) {
+							gender = Gender::Female;
 						}
 
 						SendIllusionPacket(