Remove all code from main.asm (some labeled INCBINs, like out-of-context graphics, are still present)

engine/routines/ stores isolated out-of-context routines as individual files. It might be preferable later to append them to their related engine/ files in unique little SECTIONs, relying on the linkerscript to place them appropriately; or some other organization method. In the meantime, they're now easily findable apart from main.asm's other content.

engine/routines/getbreedmonlevelgrowth.asm

@@ -0,0 +1,27 @@
+GetBreedMon1LevelGrowth: ; e698
+	ld hl, wBreedMon1Stats
+	ld de, TempMon
+	ld bc, BOXMON_STRUCT_LENGTH
+	call CopyBytes
+	callfar CalcLevel
+	ld a, [wBreedMon1Level]
+	ld b, a
+	ld a, d
+	ld e, a
+	sub b
+	ld d, a
+	ret
+
+GetBreedMon2LevelGrowth: ; e6b3
+	ld hl, wBreedMon2Stats
+	ld de, TempMon
+	ld bc, BOXMON_STRUCT_LENGTH
+	call CopyBytes
+	callfar CalcLevel
+	ld a, [wBreedMon2Level]
+	ld b, a
+	ld a, d
+	ld e, a
+	sub b
+	ld d, a
+	ret