Not THAT Slow - Update Movespeed Modifiers for Smooth Movement (#22127)

The /tg/-style movespeed_modifier datums were not incorporated into the
original smooth movement PR. While
https://github.com/Aurorastation/Aurora.3/pull/22043 restores that
functionality, the original values no longer feel good now that we're on
smooth movement. This PR halves ALL movespeed_modifier/slowdown datums,
with the exception of species-native, as a baseline before more
individual adjustments are made.

code/modules/cargo/delivery/backpack.dm

@@ -53,7 +53,7 @@
 
 /obj/item/cargo_backpack/proc/update_state(mob/user)
 	if(LAZYLEN(contained_packages))
-		slowdown = 1
+		slowdown = 0.5
 	else
 		slowdown = 0
 	update_icon()

code/modules/cargo/delivery/package.dm

@@ -18,7 +18,7 @@
 	w_class = WEIGHT_CLASS_HUGE
 	force = 15
 
-	slowdown = 1
+	slowdown = 0.5
 
 	var/delivery_point_id = ""
 	var/datum/weakref/delivery_point_sector
@@ -83,7 +83,7 @@
 		// larger mobs, such as industrials, can hold two pieces of cargo
 		if(user.species.mob_size < 12)
 			wield(user)
-			slowdown = 2
+			slowdown = 1
 		else
 			slowdown = 0