Vehicles hear exterior audio (#4815)

# About the pull request

As described in issue #4777 while vehicle interiors are intended to hear
external sounds, it is largely nonfunctional. Sounds are either not
heard or are inaudibly quiet. This is due to several smaller issues
working together.

First, interiors are not detected as interiors. In commit
0808500
the types stored in the `used_turfs` list were changed to weakrefs, but
the `is_interior()` function still checked for the old type, causing it
to always return `FALSE`:
https://github.com/cmss13-devs/cmss13/blob/5fbe14390f80225a5d295f07b9acf781fb8aa2b2/code/controllers/subsystem/interior.dm#L54-L58
Fixed by checking for the correct type.

Second, the `get_interior_by_coords()` function returned an object on
success, but returned `FALSE` on failure - which still counted as an
object. Since shuttles add turfs to `used_turfs` but don't have actual
interiors, they would pass `is_interior()` but fail
`get_interior_by_coords()`. The sound code expected any object received
at this point to be valid, but using `FALSE` would thrown an error:
https://github.com/cmss13-devs/cmss13/blob/5fbe14390f80225a5d295f07b9acf781fb8aa2b2/code/game/sound.dm#L82-L84
Fixed by returning `null` on failure.

Third, the audio was now playing but in the wrong part of the interior.
It was offset to the top-right corner because `get_middle_coords()` got
the difference between the bounds, but never actually averaged them:
https://github.com/cmss13-devs/cmss13/blob/5fbe14390f80225a5d295f07b9acf781fb8aa2b2/code/modules/vehicles/interior/interior.dm#L321
Fixed by dividing the difference by two.

Fourth, the sound playback zone was oriented incorrectly because the
width and height were transposed when creating the zone. Rectangles were
defined as width then height, but the sound subsystem was passing height
then width:
https://github.com/cmss13-devs/cmss13/blob/5fbe14390f80225a5d295f07b9acf781fb8aa2b2/code/controllers/subsystem/sound.dm#L44
Fixed by passing width then height.

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# Explain why it's good for the game

Vehicle interiors were intended to hear external sounds. This restores
that functionality.
# Testing Photographs and Procedure
<details>
<summary>Screenshots & Videos</summary>

Put screenshots and videos here with an empty line between the
screenshots and the `<details>` tags.

</details>


# Changelog
:cl:
fix: vehicle interiors can hear exterior noises
/:cl:

---------

Co-authored-by: harryob <[email protected]>

code/controllers/subsystem/interior.dm

@@ -42,7 +42,7 @@ SUBSYSTEM_DEF(interior)
 			continue
 		if(x >= bounds[1].x && x <= bounds[2].x && y >= bounds[1].y && y <= bounds[2].y)
 			return current_interior
-	return FALSE
+	return
 
 /// Checks if an atom is in an interior
 /datum/controller/subsystem/interior/proc/in_interior(loc)
@@ -51,7 +51,7 @@ SUBSYSTEM_DEF(interior)
 	if(!isturf(loc))
 		loc = get_turf(loc)
 
-	var/datum/turf_reservation/interior/reservation = SSmapping.used_turfs[loc]
+	var/datum/weakref/reservation = SSmapping.used_turfs[loc]
 
 	if(!istype(reservation))
 		return FALSE

code/controllers/subsystem/sound.dm

@@ -41,5 +41,5 @@ SUBSYSTEM_DEF(sound)
 			if(VI?.ready)
 				var/list/bounds = VI.get_middle_coords()
 				if(bounds.len >= 2)
-					hearers |= SSquadtree.players_in_range(RECT(bounds[1], bounds[2], VI.map_template.height, VI.map_template.width), bounds[3])
+					hearers |= SSquadtree.players_in_range(RECT(bounds[1], bounds[2], VI.map_template.width, VI.map_template.height), bounds[3])
 	template_queue[template] = hearers

code/modules/vehicles/interior/interior.dm

@@ -318,7 +318,7 @@
 	var/turf/min = reservation.bottom_left_coords
 	var/turf/max = reservation.top_right_coords
 
-	return list(Floor(min[1] + (max[1] - min[1])), Floor(min[2] + (max[2] - min[2])), min[3])
+	return list(Floor(min[1] + (max[1] - min[1])/2), Floor(min[2] + (max[2] - min[2])/2), min[3])
 
 /datum/interior/proc/get_middle_turf()
 	var/list/turf/bounds = get_bound_turfs()