Gym Leader Rematches!

This commit adds a large fundamental change to KEP, that being Gym Rematches.

This is achieved alongside a rework to the script that makes those post-game-gating NPCs shift around. If you add a new one, just add its constant to the lists you'll see in the Hall of Fame script.

It also fixes a few bugs:
- Fixed a bug where Cinnabar Gym loaded a fleet of Blaines. This occurred due to the way he is coded at base, and a misunderstanding I had when implementing his scaling. This is now fixed by standardising his gym script instead, while letting the gym trainers still use the old one.
- Fixed a bug where the Up-Grade NPC would not appear after beating Silph Co. 11F. However, Giovanni currently seems to have trouble with his text. This floor needs some re-coding anyway, given we need to add Jessie and James to it.

And some misc. changes:
- Changed the first Moon Stone in Mt. Moon to a Poison Stone for the Nidoking speedrunners
- Debug Mode now has a line of code to set up the post-game easily
- Changed Surge's initial battle text to Yellow's
- Added Sabrina's more accurate LGPE initial battle text, referring to the spoon she bent by accident

constants/event_constants.asm

@@ -831,7 +831,7 @@ DEF INDIGO_PLATEAU_EVENTS_END EQU const_value - 1
 
 ; Victory Road 1F events
 	const_next $910
-	const_skip
+	const EVENT_POST_GAME_ATTAINED ; Used for Gym Leader rematches, among other things.
 	const EVENT_BEAT_VICTORY_ROAD_1_TRAINER_0
 	const EVENT_BEAT_VICTORY_ROAD_1_TRAINER_1
 	const_skip 4