Tunnels are converted to forsaken on evac (#5394)

# About the pull request
the other half of #5340, fixes #4376 
Tunnels are now forsaken!
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# Explain why it's good for the game

Forsaken xenos should be able to use tunnels

# Testing Photographs and Procedure
<details>
<summary>Open me for testing</summary>


https://github.com/cmss13-devs/cmss13/assets/54422837/25f7ce72-0773-4bce-896a-800054d6b232



https://github.com/cmss13-devs/cmss13/assets/54422837/e4954940-f39e-4bda-9756-5f8da3dcc6a0



</details>


# Changelog
:cl:
fix: Tunnels are now converted to forsaken on evac.
/:cl:

code/modules/cm_aliens/structures/tunnel.dm

@@ -48,6 +48,20 @@
 	if(resin_trap)
 		qdel(resin_trap)
 
+		if(hivenumber == XENO_HIVE_NORMAL)
+			RegisterSignal(SSdcs, COMSIG_GLOB_GROUNDSIDE_FORSAKEN_HANDLING, PROC_REF(forsaken_handling))
+
+/obj/structure/tunnel/proc/forsaken_handling()
+	SIGNAL_HANDLER
+	if(is_ground_level(z))
+		hive.tunnels -= src
+		hivenumber = XENO_HIVE_FORSAKEN
+		set_hive_data(src, XENO_HIVE_FORSAKEN)
+		hive = GLOB.hive_datum[XENO_HIVE_FORSAKEN]
+		hive.tunnels += src
+
+	UnregisterSignal(SSdcs, COMSIG_GLOB_GROUNDSIDE_FORSAKEN_HANDLING)
+
 	SSminimaps.add_marker(src, z, get_minimap_flag_for_faction(hivenumber), "xenotunnel")
 
 /obj/structure/tunnel/Destroy()