Fixes stabilized red bypassing immutable slowdowns / Fixes being unable to construct fulltile objects on immutably slow things (#82250)

## About The Pull Request

- Fixes Stabilized Red extract's equipment slowdown immunity bypassing
item Immutable Slowdown

- Fixes(?) Settler equipment slowdown modifier applying to immutable
slows

- Fixes Immutable Slow being considered an object flag when it was an
item flag, causing objects to consider objects with it to be
`BLOCKS_CONSTRUCTION_DIR`

## Why It's Good For The Game

The description of Immutable Slows: 

`When players should not be able to change the slowdown of the item
(Speed potions, etc)`

Stabilized Red extracts were changing the slowdown of the item, which is
unintended.
Likewise Settler was doing the same, but that one I'm a bit more iffy
on.

Either way I suppose if things should immutably be slow, they should
immutably be slow.

## Changelog

🆑 Melbert
fix: Stabilized Red extracts no longer bypass Immutably Slow items
fix: Settler equipment speed modifier no longer applied to Immutably
Slow items
fix: Immutably Slow items no longer block construction of certain items 
/🆑

code/modules/mod/mod_clothes.dm

@@ -9,7 +9,7 @@
 	body_parts_covered = HEAD
 	heat_protection = HEAD
 	cold_protection = HEAD
-	obj_flags = IMMUTABLE_SLOW
+	item_flags = IMMUTABLE_SLOW
 
 /obj/item/clothing/suit/mod
 	name = "MOD chestplate"
@@ -28,7 +28,7 @@
 	body_parts_covered = CHEST|GROIN
 	heat_protection = CHEST|GROIN
 	cold_protection = CHEST|GROIN
-	obj_flags = IMMUTABLE_SLOW
+	item_flags = IMMUTABLE_SLOW
 
 /obj/item/clothing/gloves/mod
 	name = "MOD gauntlets"
@@ -41,7 +41,7 @@
 	body_parts_covered = HANDS|ARMS
 	heat_protection = HANDS|ARMS
 	cold_protection = HANDS|ARMS
-	obj_flags = IMMUTABLE_SLOW
+	item_flags = IMMUTABLE_SLOW
 
 /obj/item/clothing/shoes/mod
 	name = "MOD boots"
@@ -54,6 +54,5 @@
 	body_parts_covered = FEET|LEGS
 	heat_protection = FEET|LEGS
 	cold_protection = FEET|LEGS
-	obj_flags = IMMUTABLE_SLOW
-	item_flags = IGNORE_DIGITIGRADE
+	item_flags = IGNORE_DIGITIGRADE | IMMUTABLE_SLOW
 	can_be_tied = FALSE