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/link/link.asm

@@ -2212,7 +2212,8 @@ endc
 	call DelayFrames
 	xor a
 	ldh [hVBlank], a
-	inc a ; LINK_TIMECAPSULE
+	assert LINK_TIMECAPSULE == 1
+	inc a
 	ld [wLinkMode], a
 	ret
 
@@ -2285,7 +2286,7 @@ SetBitsForTimeCapsuleRequest:
 	ldh [rSC], a
 	ld a, (1 << rSC_ON) | (0 << rSC_CLOCK)
 	ldh [rSC], a
-	xor a ; LINK_TIMECAPSULE - 1
+	xor a ; LINK_NULL
 	ld [wPlayerLinkAction], a
 	ld [wChosenCableClubRoom], a
 	ret