dragon antag refactor (#28217)

* remove dragon system usage of GenericAntag

* add AntagRandomSpawn for making antags spawn at a random tile

* add AntagSpawner to make an antag spawner just spawn an entity

* add antag prototype for dragon since it never had one

* make dragon spawner a GhostRoleAntagSpawner, remove GenericAntag

* make dragon rule use AntagSelection and stuff

* remove dragon GenericAntag rule

* add back to spawn menu

---------

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

Content.Server/Antag/AntagRandomSpawnRule.cs

@@ -0,0 +1,22 @@
+using Content.Server.Antag.Components;
+using Content.Server.GameTicking.Rules;
+
+namespace Content.Server.Antag;
+
+public sealed class AntagRandomSpawnSystem : GameRuleSystem<AntagRandomSpawnComponent>
+{
+    [Dependency] private readonly SharedTransformSystem _transform = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<AntagRandomSpawnComponent, AntagSelectLocationEvent>(OnSelectLocation);
+    }
+
+    private void OnSelectLocation(Entity<AntagRandomSpawnComponent> ent, ref AntagSelectLocationEvent args)
+    {
+        if (TryFindRandomTile(out _, out _, out _, out var coords))
+            args.Coordinates.Add(_transform.ToMapCoordinates(coords));
+    }
+}