Destroy several sources of lag (#21422)

Destroys a ton of sources of lag:

- /obj/machinery/biogenerator/interact and
/obj/machinery/computer/rdconsole/attack_hand

Both of these call REF(src) constantly on their UI update, which also
happens constantly. Death by a thousand cuts

- /obj/machinery/button/ignition/attack_hand and
/obj/machinery/button/switch/holosign/attack_hand

Sleeps rather than timers, iterating the entire machinery list rather
than just storing the IDs we need at roundstart

- /obj/machinery/telecomms/update_icon and /obj/machinery/meter/process

Calling overlay updates WAY TOO MUCH. UpdateOverlays is a significant
overhead for the server at this point and the two of these combined are
responsible for a little over 20% of updates. They now should only
update overlays when necessary rather than every tick.

- NEW! /obj/machinery/disposal/proc/update and
/obj/machinery/portable_atmospherics/hydroponics/update_icon

These two were also offenders, worse than telecomms but better than
meters. They have also been brought into line.

- /mob/living/carbon/slime

Hard-del'd if grinded into slime extract less than two minutes after
being "born". Fixed by adding TIMER_DELETE_ME flag.

---------

Co-authored-by: Matt Atlas <liermattia@gmail.com>

code/modules/client/client_procs.dm

@@ -531,6 +531,9 @@ GLOBAL_LIST_INIT(localhost_addresses, list(
 		holder.owner = null
 		GLOB.staff -= src
 
+	if(mob)
+		mob.clear_important_client_contents()
+
 	SSping.currentrun -= src
 
 	QDEL_NULL(tooltips)