Adds explosion handling to experimental sensor tower (#4984)

# About the pull request

Fixes #4958 

Adds explosion handling to sensor tower.

# Explain why it's good for the game
# 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:
add: Explosion handling logic to experimental sensor tower.
fix: Explosions no longer delete experimental sensor tower.
/:cl:

code/modules/desert_dam/motion_sensor/sensortower.dm

@@ -233,6 +233,25 @@
 	..()
 	update_icon()
 
+/* Decreases the buildstate of the sensor tower and switches it off if affected by any explosion.
+Higher severity explosion will damage the sensor tower more
+*/
+/obj/structure/machinery/sensortower/ex_act(severity)
+	if(buildstate == SENSORTOWER_BUILDSTATE_WRENCH)
+		return
+	switch(severity)
+		if(0 to EXPLOSION_THRESHOLD_LOW)
+			buildstate += 1
+		if(EXPLOSION_THRESHOLD_LOW to EXPLOSION_THRESHOLD_MEDIUM)
+			buildstate = clamp(buildstate + 2, SENSORTOWER_BUILDSTATE_WORKING, SENSORTOWER_BUILDSTATE_WRENCH)
+		if(EXPLOSION_THRESHOLD_HIGH to INFINITY)
+			buildstate = 3
+	if(is_on)
+		is_on = FALSE
+		cur_tick = 0
+		stop_processing()
+	update_icon()
+
 #undef SENSORTOWER_BUILDSTATE_WORKING
 #undef SENSORTOWER_BUILDSTATE_BLOWTORCH
 #undef SENSORTOWER_BUILDSTATE_WIRECUTTERS