Finish Chief, bug fixes

This finishes Chief's event, with all the necessary components for the post-game Mewtwo fight sorted as well. I added an event the Master Ball sets for modular monologue text, for improved immersion.

I have also fixed some bugs;
- Fixed the oft-reported walking in trees bug in the Forest tileset.
- Fixed the Oak's lab computer issue by just...removing the computer. I made the map symmetrical instead, feels a lot better to look at, at least for me. I think it was meant to have an event on it or something, but I couldn't find anything, felt like I was being gaslit.
- Hopefully fixed the issue with the border blocks going weird after saving and resetting, by making the tileset directly point to the gym one, which Oak is meant to use. I am not sure how that glitch happened for ViWalls.
- Fixed the Viridian Pre-Gym text scrolling issue.

I still cannot replicate the crash bugs that some people have been experiencing and don't see anything that could be causing it.

I also changed Trampel in Victory Road to Steelix, as mentioned by Gogocrafter.

data/wild/maps/VictoryRoad1F.asm

@@ -1,7 +1,7 @@
 VictoryRoad1FWildMons:
 	def_grass_wildmons 15 ; encounter rate
 	db 34, MACHOKE
-	db 36, RHYDON
+	db 36, STEELIX
 	db 32, GOLBAT
 	db 36, SANDSLASH
 	db 39, SANDSLASH

data/wild/maps/VictoryRoad2F.asm

@@ -1,7 +1,7 @@
 VictoryRoad2FWildMons:
 	def_grass_wildmons 10 ; encounter rate
 	db 32, MACHOKE
-	db 34, TRAMPEL
+	db 34, STEELIX
 	db 36, GOLBAT
 	db 36, SANDSLASH
 	db 39, SANDSLASH

data/wild/maps/VictoryRoad3F.asm

@@ -1,7 +1,7 @@
 VictoryRoad3FWildMons:
 	def_grass_wildmons 15 ; encounter rate
 	db 34, MACHOKE
-	db 36, TRAMPEL
+	db 36, STEELIX
 	db 32, GOLBAT
 	db 42, SANDSLASH
 	db 40, VENOMOTH