Adds support for multiple callback checks for the do_after and incapacitated procs (#13057)

* do_after refactor

Update slime.dm

fix a comment

if you read this you get a cookie!

* some little tweaks

Changes a TRUE to FALSE in a comment, got confused there.

Removes the code that checks for non-callbacks in the extra_checks list and removes them. It should be up to the dev to not add non-callbacks to this list. I'd rather have it runtime instead

* check_for_true_callbacks

* CRLF to LF

Co-authored-by: SteelSlayer <SteelSlayer@users.noreply.github.com>

code/modules/mob/status_procs.dm

@@ -173,6 +173,9 @@
 /mob/proc/Stun()
 	return
 
+/mob/proc/IsStunned()
+	return stunned
+
 /mob/proc/SetStunned()
 	return