Refactors Regenerate Organs, and a few organ helpers (#74219)

## About The Pull Request

Refactors regenerate organs to be slightly more intelligent in handling
organ changes and replacements.
Noteably:
- We don't remove organs that were modified by the owner; such as
changing out your heart for a cybernetic
- We early break out of the for loop if they aren't supposed to have an
organ there and remove it
- We check for the organ already being correct, and just healing it and
continuing if it is

Also changes the names of some of the organ helpers into snake_case
### Mapping March
Ckey to receive rewards: N/A

## Why It's Good For The Game
## Changelog

---------

Co-authored-by: Jacquerel <hnevard@gmail.com>

code/modules/mod/mod_core.dm

@@ -243,7 +243,7 @@
 	var/charge_modifier = 0.1
 
 /obj/item/mod/core/ethereal/charge_source()
-	var/obj/item/organ/internal/stomach/ethereal/ethereal_stomach = mod.wearer.getorganslot(ORGAN_SLOT_STOMACH)
+	var/obj/item/organ/internal/stomach/ethereal/ethereal_stomach = mod.wearer.get_organ_slot(ORGAN_SLOT_STOMACH)
 	if(!istype(ethereal_stomach))
 		return
 	return ethereal_stomach