/datum/reagent/consumable/ethanol/New() will now treat addiction_types as a lazylist (#89801)

## About The Pull Request
Normally `addiction_types` isn't defined for any subtypes of
`/datum/reagent/consumable/ethanol`, and is instead calculated by
`/datum/reagent/consumable/ethanol/New()`.

However, the way it handles this actually overrides any previously-set
addiction types, forcing any subtypes that would want to have other
addiction types to define them in `New()` *after*
`/datum/reagent/consumable/ethanol/New()` runs.

As an example of this, take a look at
<Monkestation/Monkestation2.0#5750>. It adds a
coffee addiction to any alcoholic reagents which contain coffee - but it
had to edit `/datum/reagent/consumable/ethanol/New()` to account for the
fact that the addiction types list may not be empty.

Thing is, `addiction_types` is already sort of a lazylist - its initial
value (defined in `/datum/reagent/var/addiction_types`) is `null`, so it
was kind of asking to be used this way anyways.

So, to handle the possibility of a subtype setting other addiction
types, and additionally to make the code a little nicer by using
`addiction_types` as the lazylist it seems to want to be, I've modified
`/datum/reagent/consumable/ethanol/New()` to use `LAZYSET` when adding
the alcohol addiction.

--

I also changed it such that the alcohol addiction is only added if
`boozepwr` is any value other than `0`. This ensures that, if the
reagent in question doesn't use `boozepwr`, and has no other addiction
types, `addiction_types` will stay `null`. This saves a little bit of
memory - admittedly, not much, but still!

## Why It's Good For The Game
Subtypes of `/datum/reagent/consumable/ethanol` can now have default
addiction types other than `/datum/addiction/alcohol`.

## Changelog
No player-facing changes.

Author: LikeLakers2

code/modules/reagents/chemistry/reagents/drinks/alcohol_reagents.dm

@@ -47,7 +47,8 @@
 			name = "Natural " + name
 		if(data["boozepwr"])
 			boozepwr = data["boozepwr"]
-	addiction_types = list(/datum/addiction/alcohol = 0.05 * boozepwr)
+	if(boozepwr) // anything other than 0
+		LAZYSET(addiction_types, /datum/addiction/alcohol, 0.05 * boozepwr)
 	return ..()
 
 /datum/reagent/consumable/ethanol/on_mob_life(mob/living/carbon/drinker, seconds_per_tick, times_fired)