This tail refactor turned into an organ refactor. Funny how that works. (#67017)

* Fuck you (refactors ur tails)

* Errors

* Wow. Pain.

* Fixes up probably everything

* finish up here

* Fixes hard del maybe

* original owner hard del

* garbage collection runtime

* suck my peen byond

* Mapped tails

* motherfucker.

* motherrfucker. again.

* Whooopppppsie

* yeah bad idea

* Turns out external organs literally just sat in nullspace forever if their parent was deleted, and didnt Remove() themselves, causing harddels.

* So anyways I repathed all organs

* Fixes

* really.

* unit test... test

* unit test-test but it passes linters this time because im a moh-ron

* I've lost track of what im doing at this point

* Hopefully fixes hard del?

* meh

* Update code/datums/dna.dm

* things n stuff

* repath from master pull

code/modules/client/preferences/_preference.dm

@@ -105,6 +105,10 @@ GLOBAL_LIST_INIT(preference_entries_by_key, init_preference_entries_by_key())
 	/// will show the feature as selectable.
 	var/relevant_species_trait = null
 
+	/// If the selected species has this in its /datum/species/var/external_organs,
+	/// will show the feature as selectable.
+	var/relevant_external_organ = null
+
 /// Called on the saved input when retrieving.
 /// Also called by the value sent from the user through UI. Do not trust it.
 /// Input is the value inside the savefile, output is to tell other code
@@ -318,7 +322,7 @@ GLOBAL_LIST_INIT(preference_entries_by_key, init_preference_entries_by_key())
 	SHOULD_CALL_PARENT(TRUE)
 	SHOULD_NOT_SLEEP(TRUE)
 
-	if (!isnull(relevant_mutant_bodypart) || !isnull(relevant_species_trait))
+	if (!isnull(relevant_mutant_bodypart) || !isnull(relevant_species_trait) || !isnull(relevant_external_organ))
 		var/species_type = preferences.read_preference(/datum/preference/choiced/species)
 
 		var/datum/species/species = new species_type