Bools and returns super-pr (#53221)

Replaces like 70-80% of 0 and such, as a side effect cleaned up a bunch of returns
Edit: Most left out ones are in mecha which should be done in mecha refactor already
Oh my look how clean it is

Co-authored-by: TiviPlus <TiviPlus>
Co-authored-by: Couls <coul422@gmail.com>

code/modules/modular_computers/computers/item/computer.dm

@@ -222,11 +222,11 @@
 /obj/item/modular_computer/process()
 	if(!enabled) // The computer is turned off
 		last_power_usage = 0
-		return 0
+		return
 
 	if(obj_integrity <= integrity_failure * max_integrity)
 		shutdown_computer()
-		return 0
+		return
 
 	if(active_program && active_program.requires_ntnet && !get_ntnet_status(active_program.requires_ntnet_feature))
 		active_program.event_networkfailure(0) // Active program requires NTNet to run but we've just lost connection. Crash.