Wieldable/two-handed weapons (#4554)

* wielding kinda works

* rough out all the edges, wielding works nicely

* popups + loc

* increase damage & extra damage against whitelist

* small fixes

* forgot to actually do that

* reviews

* reviews + thing

* use resistances and not extradamageagainstwhitelist

* slashy

* make increasedamageonwield and melee hit events work with modifiersets

* Silly individual

Content.Shared/Damage/DamageSpecifier.cs

@@ -183,6 +183,24 @@ namespace Content.Shared.Damage
             return newDamage;
         }
 
+        /// <summary>
+        ///     Reduce (or increase) damages by applying multiple modifier sets.
+        /// </summary>
+        /// <param name="damageSpec"></param>
+        /// <param name="modifierSets"></param>
+        /// <returns></returns>
+        public static DamageSpecifier ApplyModifierSets(DamageSpecifier damageSpec, IEnumerable<DamageModifierSet> modifierSets)
+        {
+            DamageSpecifier newDamage = new(damageSpec);
+            foreach (var set in modifierSets)
+            {
+                // this is probably really inefficient. just don't call this in a hot path I guess.
+                newDamage = ApplyModifierSet(newDamage, set);
+            }
+
+            return newDamage;
+        }
+
         /// <summary>
         ///     Remove any damage entries with zero damage.
         /// </summary>