use weighted random for ninja threats (#20469)

* change threats to be weighted random and a little cleanup

* ninja rule stores weighted random id for threats

* move threats out of the rule and into weighted random

---------

Co-authored-by: deltanedas <@deltanedas:kde.org>

Resources/Prototypes/GameRules/midround.yml

@@ -14,8 +14,4 @@
     - TerrorObjective
     - NinjaSurviveObjective
   - type: NinjaRule
-    threats:
-    - announcement: terror-dragon
-      rule: Dragon
-    - announcement: terror-revenant
-      rule: RevenantSpawn
+    threats: NinjaThreats

Resources/Prototypes/threats.yml

@@ -0,0 +1,16 @@
+# threats called in by ninja hacking comms console
+- type: weightedRandom
+  id: NinjaThreats
+  weights:
+    Dragon: 1
+    Revenant: 1
+
+- type: threat
+  id: Dragon
+  announcement: terror-dragon
+  rule: Dragon
+
+- type: threat
+  id: Revenant
+  announcement: terror-revenant
+  rule: RevenantSpawn