[MIRROR] removes dextrous_hud_type and healable var [MDB IGNORE] (#22992)

* removes dextrous_hud_type and healable var (#77244)

## About The Pull Request

I was working on some basic mob stuff and noticed this is a little
messy, so I made these changes separately.
I removed ``dextrous_hud_type`` because ``hud_type`` exists and can just
be used instead.
I also removed the ``healable`` var, because it was incorrectly used
(with the expectation that basic mobs had it too). Instead it will rely
on the mob being Organic, the check right under it, and I gave mob
biotypes to mobs that were not healable and had no biotype already.
I made a new biotype for slimes because I didn't find any other ones
that fit it (and gave it to slimepeople), but it is not used anywhere
other than to prevent them from healing from sutures, as I didn't want
to just set it to NONE. Thought this may be useful for the future.

## Why It's Good For The Game

``healable`` is checked on simple animals and basic mobs, despite basic
mobs not having this var. I do not want to add this var to basic mobs
either, I think checking for them being organic makes much more sense
and avoids having to make basic mobs less basic.

## Changelog

Nothing player-facing.

* removes dextrous_hud_type and healable var

* Modular

---------

Co-authored-by: John Willard <53777086+JohnFulpWillard@users.noreply.github.com>
Co-authored-by: Giz <13398309+vinylspiders@users.noreply.github.com>

code/modules/mob/living/basic/space_fauna/demon/demon.dm

@@ -19,7 +19,7 @@
 	icon_state = "demon"
 	icon_living = "demon"
 
-	mob_biotypes = MOB_UNDEAD|MOB_HUMANOID // undead is important because it means we can't be healed with sutures and the like. keep this in mind if you ever decide to change this
+	mob_biotypes = MOB_BEAST|MOB_HUMANOID
 	status_flags = CANPUSH
 
 	combat_mode = TRUE