More abilities, refactor stealing held items

Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/Stall.cs

@@ -0,0 +1,16 @@
+namespace PkmnLib.Plugin.Gen7.Scripts.Abilities;
+
+/// <summary>
+/// Stall is an ability that makes the Pokémon move last in its priority bracket.
+///
+/// <see href="https://bulbapedia.bulbagarden.net/wiki/Stall_(Ability)">Bulbapedia - Stall</see>
+/// </summary>
+[Script(ScriptCategory.Ability, "stall")]
+public class Stall : Script
+{
+    /// <inheritdoc />
+    public override void ChangeSpeed(ITurnChoice choice, ref uint speed)
+    {
+        speed = 0;
+    }
+}