Refactor gib code to use bitflags and have documentation (#78754)

## About The Pull Request
This takes all the gib related procs:
- `gib()`
- `spawn_gibs()` 
- `spill_organs()`
- `spread_bodyparts()`

And adds heavy documentation that communicates what the procs are used
for and how the different bitflags affect them. The difference is
noticeable:

`gib(TRUE, FALSE, FALSE, null)` vs `gib(DROP_ORGANS|DROP_BODYPARTS)`

The code is now much more legible which is important considering it's
used in a lot of places!

Another robust change, is that we had several places in the code where
there were double negatives like so:

```
/mob/living/carbon/spill_organs(no_brain, no_organs, no_bodyparts)
	if(!no_bodyparts) // DOUBLE NEGATIVES ARE BAD M'KAY?!?
		// do stuff here
```

This is a mindfuck to untangle. I inverted a lot of these parts so we
don't lose our sanity.

Last thing that was changed was a big `if()` loop in the `spill_organ()`
proc. This was refactored to just be a simple `for` loop with `continue`
statements where we needed to skip enabled bitflags. It's now shorter
and cleaner than before.

The only slight gameplay change this affects is that gibbing a mob now
guarantees to drop all items unless the `DROP_ITEMS` bitflag is
deliberately omitted. Some places like admin gib self, we don't want
this to happen.

## Why It's Good For The Game
Gib code is very old. (~15 years) People kept adding more arguments to
the procs when it should have been a bitflag initially. By doing it this
way, there is more flexibility and readability when it comes to adding
new code in the future.

## Changelog
🆑
refactor: Refactor gib code to be more robust.
qol: Gibbing a mob will result in all items being dropped instead of
getting deleted. There are a few exceptions (like admin gib self) where
this will not take place.
/🆑

code/modules/wiremod/shell/drone.dm

@@ -32,7 +32,7 @@
 /mob/living/circuit_drone/updatehealth()
 	. = ..()
 	if(health < 0)
-		gib(no_brain = TRUE, no_organs = TRUE, no_bodyparts = TRUE)
+		gib()
 
 /mob/living/circuit_drone/welder_act(mob/living/user, obj/item/tool)
 	. = ..()