Generalize ResistanceSets into DamageModifierSets (#4619)

* generalize ResistanceSets into DamageModifierSets

* remove unneeded test prototype

Content.Shared/Damage/DamageModifierSet.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using Content.Shared.Damage.Prototypes;
+using Robust.Shared.Serialization;
+using Robust.Shared.Serialization.Manager.Attributes;
+using Robust.Shared.Serialization.TypeSerializers.Implementations.Custom.Prototype.Dictionary;
+
+namespace Content.Shared.Damage
+{
+    /// <summary>
+    ///     A set of coefficients or flat modifiers to damage types.. Can be applied to <see cref="DamageSpecifier"/> using <see
+    ///     cref="DamageSpecifier.ApplyModifierSet(DamageSpecifier, DamageModifierSet)"/>. This can be done several times as the
+    ///     <see cref="DamageSpecifier"/> is passed to it's final target. By default the receiving <see cref="DamageableComponent"/>, will
+    ///     also apply it's own <see cref="DamageModifierSet"/>.
+    /// </summary>
+    [DataDefinition]
+    [Serializable, NetSerializable]
+    public class DamageModifierSet
+    {
+        [DataField("coefficients", customTypeSerializer: typeof(PrototypeIdDictionarySerializer<float, DamageTypePrototype>))]
+        public Dictionary<string, float> Coefficients = new();
+
+        [DataField("flatReductions", customTypeSerializer: typeof(PrototypeIdDictionarySerializer<float, DamageTypePrototype>))]
+        public Dictionary<string, float> FlatReduction = new();
+    }
+}