Cleans up chemical reaction & reagent look up code (#95281)

## About The Pull Request
- Removed global list `fake_reagent_blacklist` in favour of
`abstract_type`. Saved memory
- Removed proc `get_chemical_reaction()` in favor of
`GLOB.chemical_reaction_list`. No proc overhead and faster access
- Remove unused proc `remove_chemical_reaction()`
- Removed proc `find_reagent()` in favour of
`GLOB.chemical_reagents_list`. No proc overhead and faster access
- Directly access name of reagents via `::` operator from typepaths
instead of looking up the datum in global chemical reagents list for
some operations. Faster variable access
- Removed unit test `reagent_id_typos`. The typepaths will error at
compile time because they aren't strings so there's no need for this
test

## Changelog
🆑
code: cleaned up code pertaining to reagent & reaction lookup
/🆑

code/controllers/subsystem/processing/reagents.dm

@@ -13,8 +13,6 @@ PROCESSING_SUBSYSTEM_DEF(reagents)
 /datum/controller/subsystem/processing/reagents/Initialize()
 	//So our first step isn't insane
 	previous_world_time = world.time
-	///Blacklists these reagents from being added to the master list. the exact type only. Children are not blacklisted.
-	GLOB.fake_reagent_blacklist = list(/datum/reagent/medicine/c2, /datum/reagent/medicine, /datum/reagent/reaction_agent)
 	//Build GLOB lists - see holder.dm
 	build_chemical_reactions_lists()
 	return SS_INIT_SUCCESS