Cleanup factions code (#11075)

Co-authored-by: Kara <lunarautomaton6@gmail.com>

Content.Server/NPC/FactionData.cs

@@ -0,0 +1,13 @@
+namespace Content.Server.NPC;
+
+/// <summary>
+/// Cached data for the faction prototype. Can be modified at runtime.
+/// </summary>
+public sealed class FactionData
+{
+    [ViewVariables]
+    public HashSet<string> Friendly = new();
+
+    [ViewVariables]
+    public HashSet<string> Hostile = new();
+}