Split and clarify global lists of processing vs non-processing machinery. (#5307)

* Renaming local var 'machines' to avoid confusion with the global var of same name.

* Delete the unused process scheduler machinery.dm file.  Long since replaced with SSmachines

* Split and clarify global lists of processing vs non-processing machinery.

- Renamed the list of processing machinery from "machines" to "processing_machines"
- Added new global list "machines" to be a list of all machines.
- Since nearly every reference to machines actually wanted to iterate over all machines anyway, this works out great.

code/controllers/subsystems/machines.dm

@@ -90,10 +90,10 @@ SUBSYSTEM_DEF(machines)
 	msg += "PO:[round(cost_power_objects,1)]"
 	msg += "} "
 	msg += "PI:[global.pipe_networks.len]|"
-	msg += "MC:[global.machines.len]|"
+	msg += "MC:[global.processing_machines.len]|"
 	msg += "PN:[global.powernets.len]|"
 	msg += "PO:[global.processing_power_items.len]|"
-	msg += "MC/MS:[round((cost ? global.machines.len/cost_machinery : 0),0.1)]"
+	msg += "MC/MS:[round((cost ? global.processing_machines.len/cost_machinery : 0),0.1)]"
 	..(jointext(msg, null))
 
 /datum/controller/subsystem/machines/proc/process_pipenets(resumed = 0)
@@ -115,7 +115,7 @@ SUBSYSTEM_DEF(machines)
 
 /datum/controller/subsystem/machines/proc/process_machinery(resumed = 0)
 	if (!resumed)
-		src.current_run = global.machines.Copy()
+		src.current_run = global.processing_machines.Copy()
 
 	var/list/current_run = src.current_run
 	while(current_run.len)
@@ -125,7 +125,7 @@ SUBSYSTEM_DEF(machines)
 			if(M.use_power)
 				M.auto_use_power()
 		else
-			global.machines.Remove(M)
+			global.processing_machines.Remove(M)
 			if(!QDELETED(M))
 				M.is_processing = null
 		if(MC_TICK_CHECK)