Bill's Garden, add Rowan NPC

Rowan NPC added to Cinnabar Lab, just a little cute thing.

Bill's Garden could see many revisions, what's here is the bare minimum. Here's what's done:
- Nidorino NPC blocks it off and is unlocked in the post-game. This currently contradicts the myth - I have a plan for this soon.
- Wild Pokemon are the "non-reproducibles" given in Stadium; starters and eevee are mandatory given those were common in the myth
- Hisui forms should be added when possible
- I had to remake Martha's map in the forest tileset so leaving would be possible
- Everything is at a point where it functions

constants/hide_show_constants.asm

@@ -247,4 +247,5 @@ DEF SHOW EQU $15
 	const HS_ROUTE_1_OAK				; EB
 	const HS_MT_MOON_CRATER_GUARD		; EC
 	const HS_MANSION_GUARD				; ED
+	const HS_BILLS_NIDORINO				; EE
 DEF NUM_HS_OBJECTS EQU const_value