fix: Fixes various memory leaks and spells (#1786)

### Summary
- Fixes various memory leaks related to spells
- Fixes Spell Plague
- Added ability to determine if `sdi` should take effect for Spell Damage.
- Fixes animal form timer ticking non-stop while logged out.

Projects/UOContent/Spells/Second/Protection.cs

@@ -15,8 +15,8 @@ namespace Server.Spells.Second
             Reagent.SulfurousAsh
         );
 
-        private static readonly Dictionary<Mobile, Tuple<ResistanceMod, DefaultSkillMod>> _table =
-            new();
+        // TODO: Cleanup periodically if players have logged out for a while
+        private static readonly Dictionary<Mobile, Tuple<ResistanceMod, DefaultSkillMod>> _table = new();
 
         public ProtectionSpell(Mobile caster, Item scroll = null) : base(caster, scroll, _info)
         {