[MIRROR] Adds SIGNAL_HANDLER and SIGNAL_HANDLER_DOES_SLEEP to prevent signal callbacks from blocking (#430)

* Adds SIGNAL_HANDLER and SIGNAL_HANDLER_DOES_SLEEP to prevent signal callbacks from blocking (#52761)

Adds SIGNAL_HANDLER, a macro that sets SHOULD_NOT_SLEEP(TRUE). This should ideally be required on all new signal callbacks.

Adds BLOCKING_SIGNAL_HANDLER, a macro that does nothing except symbolize "this is an older signal that didn't necessitate a code rewrite". It should not be allowed for new work.

This comes from discussion around #52735, which yields by calling input, and (though it sets the return type beforehand) will not properly return the flag to prevent attack from slapping.

To fix 60% of the yielding cases, WrapAdminProcCall no longer waits for another admin's proc call to finish. I'm not an admin, so I don't know how many behinds this has saved, but if this is problematic for admins I can just make it so that it lets you do it anyway. I'm not sure what the point of this babysitting was anyway.

Requested by @optimumtact.
Changelog

cl
admin: Calling a proc while another admin is calling one will no longer wait for the first to finish. You will simply just have to call it again.
/cl

* Adds SIGNAL_HANDLER and SIGNAL_HANDLER_DOES_SLEEP to prevent signal callbacks from blocking

Co-authored-by: Jared-Fogle <35135081+Jared-Fogle@users.noreply.github.com>

code/modules/mining/machine_processing.dm

@@ -48,6 +48,8 @@
 	* oldLoc - the old location that `target` was at before moving onto `source`.
 */
 /obj/machinery/mineral/proc/pickup_item(datum/source, atom/movable/target, atom/oldLoc)
+	SIGNAL_HANDLER
+
 	return
 
 /// Generic unloading proc. Takes an atom as an argument and forceMove's it to the turf adjacent to this machine in the `output_dir` direction.