valid_subtypes proc (#93541)

## About The Pull Request
discussed in #93439, a generic proc for getting a list of all types
minus abstract types.
applies this to most instances of a for loop that currently filters out
abstract types

it SHOULD be a nothing burger for performance, however I have not bench
marked the difference. (also testing, there is a total of 7 calls in
init to it)

code/controllers/subsystem/processing/instruments.dm

@@ -36,10 +36,8 @@ PROCESSING_SUBSYSTEM_DEF(instruments)
 	songs -= S
 
 /datum/controller/subsystem/processing/instruments/proc/initialize_instrument_data()
-	for(var/path in subtypesof(/datum/instrument))
+	for(var/path in valid_subtypesof(/datum/instrument))
 		var/datum/instrument/I = path
-		if(initial(I.abstract_type) == path)
-			continue
 		I = new path
 		I.Initialize()
 		if(!I.id)