Adds Slime overcrowding because my byond client died once when flying over xenobio (#88935)

## About The Pull Request

Basically if there's too many slimes on a single turf, the slime will
not split.

The define I set is 2 (which can change) so you can still reasonably
spam a few monkeys inside a 3x3 cell and expect the slimes to split.

Overcrowding isn't really meant to stop people from doing xenobio like
this, it's to stop instances where people add way too many monkeys and
in 30 minutes everyone's clients turn into a powerpoint when entering
xenobiology. Basically to prevent this from happening.

```
ADMIN LOG: '(thesharkenning)'/(white wolf) deleted all instances of type or subtype of /mob/living/basic/slime (979 instances deleted) 
ADMIN LOG: '(thesharkenning)'/(white wolf) deleted all instances of type or subtype of /mob/living/basic/slime (641 instances deleted) 
ADMIN LOG: '(thesharkenning)'/(white wolf) deleted all instances of type or subtype of /mob/living/basic/slime (962 instances deleted)
```

## Why It's Good For The Game

I'm sure it's hell on the server too, but it's definitely something that
makes byond cry. You don't need a whole lot of time: just a lot of
monkeys and a single slime.

## Changelog

🆑
fix: Fixes uncapped xenobio slime multiplication which can easily result
in hundreds of slimes.
/🆑

code/modules/mob/living/basic/slime/actions.dm

@@ -77,6 +77,7 @@
 
 ///Splits the slime into multiple children if possible
 /mob/living/basic/slime/proc/reproduce()
+
 	if(stat != CONSCIOUS)
 		balloon_alert(src, "not conscious!")
 		return
@@ -92,6 +93,19 @@
 		balloon_alert(src, "need growth!")
 		return
 
+	var/list/friends_list = list()
+	for(var/mob/living/basic/slime/friend in loc)
+		if(QDELETED(friend))
+			continue
+		if(friend == src)
+			continue
+		friends_list += friend
+
+	overcrowded = length(friends_list) >= SLIME_OVERCROWD_AMOUNT
+	if(overcrowded)
+		balloon_alert(src, "overcrowded!")
+		return
+
 	var/list/babies = list()
 	var/new_nutrition = round(nutrition * 0.9)
 	var/new_powerlevel = round(powerlevel / 4)

code/modules/mob/living/basic/slime/slime.dm

@@ -66,6 +66,9 @@
 	///Our slime's current mood
 	var/current_mood = SLIME_MOOD_NONE
 
+	///If the slime is currently overcrowded and unable to reproduce.
+	var/overcrowded = FALSE
+
 	///The number of /obj/item/slime_extract's the slime has left inside
 	var/cores = 1
 	///Chance of mutating, should be between 25 and 35
@@ -243,6 +246,8 @@
 
 		if(SLIME_MAX_POWER)
 			. += span_boldwarning("It is radiating with massive levels of electrical activity!")
+	if(overcrowded)
+		. += span_warning("It seems too overcroweded to properly reproduce!")
 
 ///Changes the slime's current life state
 /mob/living/basic/slime/proc/set_life_stage(new_life_stage = SLIME_LIFE_STAGE_BABY)