Nukes get_modified_bleed_rate() and just use cached_bleed_rate instead (#92621)

## About The Pull Request

Port of my changes from [Monkestation/Monkestation2.0@`c54fc87`
(#7295)](https://github.com/Monkestation/Monkestation2.0/pull/7295/commits/c54fc872bfe767238a02da2b8bb5efdeb93a8526)

This nukes `/obj/item/bodypart/proc/get_modified_bleed_rate()`, instead
everything just uses the `cache_bleed_rate` var - `refresh_bleed_rate()`
will now take into account body position and grasping in the same way
`get_modified_bleed_rate` did.

(Un)grasping a limb already called `refresh_bleed_rate()` anyways, so
the only other change needed was making
`COMSIG_LIVING_SET_BODY_POSITION` also call it.

code/game/objects/items/stacks/medical.dm

@@ -273,7 +273,7 @@
 
 		var/datum/wound/burn/flesh/any_burn_wound = locate() in affecting.wounds
 		var/can_heal_burn_wounds = (flesh_regeneration || sanitization) && any_burn_wound?.can_be_ointmented_or_meshed()
-		var/can_suture_bleeding = stop_bleeding && affecting.get_modified_bleed_rate() > 0
+		var/can_suture_bleeding = stop_bleeding && affecting.cached_bleed_rate > 0
 		var/brute_to_heal = heal_brute && affecting.brute_dam > 0
 		var/burn_to_heal = heal_burn && affecting.burn_dam > 0
 
@@ -487,7 +487,7 @@
 		if(heal_end_sound)
 			playsound(patient, heal_end_sound, 75, TRUE, MEDIUM_RANGE_SOUND_EXTRARANGE)
 
-	if(limb.get_modified_bleed_rate())
+	if(limb.cached_bleed_rate)
 		add_mob_blood(patient)
 	limb.apply_gauze(src)