Add more assert cases in the codebase (#1115)

* Add assert for FACING_GRASS_1 and FACING_GRASS_2

* Add more assert cases

* Add assert for HP bar colors

* Assert LINK_NULL == 0

* Fix assert syntax

* Add asserts for WILD_BATTLE == 1

* Add additional WILD assert

- I need to sleep more...

* Revert asserts for WILD_BATTLE and LINK_NULL

* Commit suggested changes

* Add more assert cases

* Fix syntax error

engine/overworld/map_object_action.asm

@@ -275,8 +275,8 @@ SetFacingBoulderDust:
 	and 2
 	ld a, FACING_BOULDER_DUST_1
 	jr z, .ok
-	inc a
 	assert FACING_BOULDER_DUST_1 + 1 == FACING_BOULDER_DUST_2
+	inc a
 .ok
 	ld [hl], a
 	ret
@@ -291,8 +291,8 @@ SetFacingGrassShake:
 	and 4
 	ld a, FACING_GRASS_1
 	jr z, .ok
-	inc a ; FACING_GRASS_2
-
+	assert FACING_GRASS_1 + 1 == FACING_GRASS_2
+	inc a
 .ok
 	ld [hl], a
 	ret