feat: Integrate BossesHelper's 'set_boss_seed' into 'SeedRandom' command

Author: psyGamer

CelesteTAS-EverestInterop/Source/Gameplay/DesyncFix/SeededRandomness.cs

@@ -86,6 +86,9 @@ private static void Initialize() {
         if (ModUtils.IsInstalled("AurorasHelper")) {
             handlers.Add(new AurorasHelperHandler());
         }
+        if (ModUtils.IsInstalled("BossesHelper")) {
+            handlers.Add(new BossesHelperHandler());
+        }
         if (ModUtils.IsInstalled("PandorasBox")) {
             handlers.Add(new PandorasBoxTileGlitcherHandler());
         }
@@ -551,6 +554,25 @@ public override void PreUpdate() {
         }
     }
 
+    /// Alias for the 'set_boss_seed' console command
+    public class BossesHelperHandler : Handler {
+        public override string Name => "BossesHelper_Shared";
+
+        private readonly FieldInfo? f_TASSeed = ModUtils.GetField("BossesHelper", "Celeste.Mod.BossesHelper.BossesHelperModule", "TASSeed");
+
+        public override void Reset() {
+            if (ModUtils.GetModule("BossesHelper") is { } bossModule && f_TASSeed != null) {
+                f_TASSeed.SetValue(bossModule, 0);
+            }
+        }
+        public override void PreUpdate() {
+            if (ModUtils.GetModule("BossesHelper") is { } bossModule && f_TASSeed != null && NextSeed(out int seed)) {
+                f_TASSeed.SetValue(bossModule, seed);
+                AssertNoSeedsRemaining();
+            }
+        }
+    }
+
     public class PandorasBoxTileGlitcherHandler : Handler {
         public override string Name => "PandorasBox_TileGlitcher";