Assorted minor alt-click reskinning fixes, primarily context-based (#83105)

## About The Pull Request

This is a collection of tiny alt-click context fixes that I found during
testing #82920, but I felt were not right to put in there.
Most of the following explanation is for posterity, like they're mostly
one-liners, there's only so much explanation to do.

First off, the emotion mask would reset `current_skin` for infinite
reskinning, while we have the `INFINITE_RESKIN` flag:

https://github.com/tgstation/tgstation/blob/0c562fd74299f8ce92a81c0a932b8ec4862189af/code/modules/clothing/masks/costume.dm#L16-L19
We set this to `INFINITE_RESKIN` for sanity's sake.

Then, `/obj/item/clothing/under/add_context(...)` would call its parent,
but sometimes return `NONE` when its parent returned
`CONTEXTUAL_SCREENTIP_SET`:

https://github.com/tgstation/tgstation/blob/0c562fd74299f8ce92a81c0a932b8ec4862189af/code/modules/clothing/under/_under.dm#L83
This is bad, because reskinning context is handled on the parent
(`/obj/item`), and we have an item inheriting this which can be
reskinned, the mech pilot's suit:

https://github.com/tgstation/tgstation/blob/0c562fd74299f8ce92a81c0a932b8ec4862189af/code/modules/clothing/under/costume.dm#L224-L240
So we make this return the parent return value rather than `NONE`:
```dm
return changed ? CONTEXTUAL_SCREENTIP_SET : .
```

Next up, `/obj/item/clothing/accessory/add_context(...)` would never
actually call the parent and thus neither the reskinning context. It
also checks for whether you have an item in your active hand when
context is added, even though the context it adds actually only applies
when the accessory itself is in your active hand.

https://github.com/tgstation/tgstation/blob/0c562fd74299f8ce92a81c0a932b8ec4862189af/code/modules/clothing/under/accessories/_accessories.dm#L205-L210
So we instead make it call the parent first, check for whether the
accessory itself is in our active hand, and return the parent value if
not:
```dm
/obj/item/clothing/accessory/add_context(atom/source, list/context, obj/item/held_item, mob/user)
	. = ..()
	if(held_item != source)
		return .
	(...)
```
This resolves our issue.

We're almost there!
`/obj/item/reagent_containers/spray/medical/add_context(...)` exists,
but is entirely redundant due to this now being handled on the base
item, and also misses some of the checks it has.

https://github.com/tgstation/tgstation/blob/0c562fd74299f8ce92a81c0a932b8ec4862189af/code/modules/reagents/reagent_containers/spray.dm#L442-L447
So we just remove it.

Finally, what is to me the funniest one:

https://github.com/tgstation/tgstation/blob/9145ecb7e1e44635a1056fc704adfa3d764325e6/code/game/objects/items_reskin.dm#L8-L9
To add reskinning context, we check `item_flags` for `INFINITE_RESKIN`,
while it is actually on `obj_flags`.
So, instead, we were checking for the equivalent value in `item_flags`,
being `IN_STORAGE`.

https://github.com/tgstation/tgstation/blob/9145ecb7e1e44635a1056fc704adfa3d764325e6/code/__DEFINES/obj_flags.dm#L15

https://github.com/tgstation/tgstation/blob/9145ecb7e1e44635a1056fc704adfa3d764325e6/code/__DEFINES/obj_flags.dm#L34
And thus reskinning context for infinitely reskinnables would only show
up if they were in storage.
For now, we just update this to use `obj_flags` instead.

That's everything I found so far, which this should all fix.
## Why It's Good For The Game

Having working item usage context tends to be a good thing.
## Changelog
🆑
fix: Emotion masks no longer use a janky workaround for infinite
reskinning.
fix: Mech pilot suit shows reskinning usage context correctly.
fix: Accessories show "wear above/below suit" usage context
appropriately.
fix: Accessories don't block reskinning usage context when they
shouldn't.
fix: Showing reskinning usage context cares about the infinite
reskinning flag, rather than whether it's in storage or not.
del: Removed redundant reskinning usage context code from medical
sprays, now shows reskinning usage context like other reskinnables.
/🆑

code/game/objects/items.dm

@@ -288,7 +288,7 @@
 	if(!unique_reskin)
 		return
 
-	if(current_skin && !(item_flags & INFINITE_RESKIN))
+	if(current_skin && !(obj_flags & INFINITE_RESKIN))
 		return
 
 	context[SCREENTIP_CONTEXT_ALT_LMB] = "Reskin"

code/modules/clothing/masks/costume.dm

@@ -4,6 +4,7 @@
 	icon_state = "joy"
 	clothing_flags = MASKINTERNALS
 	flags_inv = HIDESNOUT
+	obj_flags = parent_type::obj_flags | INFINITE_RESKIN
 	unique_reskin = list(
 			"Joy" = "joy",
 			"Flushed" = "flushed",
@@ -16,7 +17,6 @@
 /obj/item/clothing/mask/joy/reskin_obj(mob/user)
 	. = ..()
 	user.update_worn_mask()
-	current_skin = null//so we can infinitely reskin
 
 /obj/item/clothing/mask/mummy
 	name = "mummy mask"

code/modules/clothing/under/_under.dm

@@ -66,6 +66,7 @@
 	. = ..()
 
 	var/changed = FALSE
+
 	if(isnull(held_item) && has_sensor == HAS_SENSORS)
 		context[SCREENTIP_CONTEXT_RMB] = "Toggle suit sensors"
 		changed = TRUE
@@ -86,7 +87,7 @@
 		context[SCREENTIP_CONTEXT_ALT_LMB] =  "Wear [adjusted == ALT_STYLE ? "normally" : "casually"]"
 		changed = TRUE
 
-	return changed ? CONTEXTUAL_SCREENTIP_SET : NONE
+	return changed ? CONTEXTUAL_SCREENTIP_SET : .
 
 
 /obj/item/clothing/under/worn_overlays(mutable_appearance/standing, isinhands = FALSE)

code/modules/clothing/under/accessories/_accessories.dm

@@ -210,8 +210,9 @@
 	. += "It can be worn above or below your suit. Right-click to toggle."
 
 /obj/item/clothing/accessory/add_context(atom/source, list/context, obj/item/held_item, mob/user)
-	if(!isnull(held_item))
-		return NONE
+	. = ..()
+	if(held_item != source)
+		return .
 
 	context[SCREENTIP_CONTEXT_RMB] = "Wear [above_suit ? "below" : "above"] suit"
 	return CONTEXTUAL_SCREENTIP_SET

code/modules/reagents/reagent_containers/spray.dm

@@ -438,15 +438,6 @@
 						"Yellow" = "sprayer_med_yellow",
 						"Blue" = "sprayer_med_blue")
 
-
-/obj/item/reagent_containers/spray/medical/add_context(atom/source, list/context, obj/item/held_item, mob/user)
-	. = ..()
-
-	if(!current_skin)
-		context[SCREENTIP_CONTEXT_ALT_LMB] = "Reskin"
-		return CONTEXTUAL_SCREENTIP_SET
-
-
 /obj/item/reagent_containers/spray/medical/reskin_obj(mob/M)
 	..()
 	switch(icon_state)