fix: Removes scale speed by dex for monsters, fixes NPC movement/thinking speed (#1019)

* Removes scaled speed by dex for monsters
* Changes scaled speed by dex for pets (HS+ expansion) to be 400ms -> 100ms between 50 -> 200 dex
* Removes speed changes that were broken for various mobs
* Combines "Legacy" speed and renames the class to `NPCSpeeds`
* Creates speed "classes" (slow, medium, fast, very fast)
* Introduces a new overridable property `SpeedClass`. Register a new speed class using `NPCSpeeds.Register()` and then set the speed class to bulk/mass apply speeds.

Order of speed determination:
1. SpeedMod
2. SpeedClass property (not null)
3. SpeedClass entry in Data\npc-speeds.json for that type
4. "Fast" (200ms Active, 400ms Passive)

Projects/UOContent/Mobiles/NPCSpeeds.cs

@@ -0,0 +1,102 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text.Json.Serialization;
+using Server.Json;
+
+namespace Server.Mobiles;
+
+public static class NPCSpeeds
+{
+    private const string _tablePath = "Data/npc-speeds.json";
+    private static Dictionary<Type, SpeedClassEntry> _speedsByType = new();
+    private static Dictionary<string, SpeedClassEntry> _speedsByName = new();
+
+    // Enabled for pets on HS+
+    public static bool ScaleSpeedByDex { get; private set; }
+    public static double MinDelay { get; private set; }
+    public static double MaxDelay { get; private set; }
+    public static int MinDex { get; private set; }
+    public static int MaxDex { get; private set; }
+
+    // Time period to lock NPCs into idling
+    public static int MinIdleSeconds { get; private set; }
+    public static int MaxIdleSeconds { get; private set; }
+
+    public static void GetSpeeds(BaseCreature bc, out double activeSpeed, out double passiveSpeed)
+    {
+        // Used for scaling pet's speed by dex in HS+
+        if (bc.ScaleSpeedByDex)
+        {
+            var maxDex = MaxDex;
+            double min = MinDelay;
+            double max = MaxDelay;
+            var dex = Math.Clamp(bc.Dex, MinDex, maxDex);
+
+            activeSpeed = Math.Max(max - (max - min) * ((double)dex / maxDex), min);
+            passiveSpeed = activeSpeed * 2;
+            return;
+        }
+
+        if (bc.SpeedClass != null && _speedsByName.TryGetValue(bc.SpeedClass, out var sp) ||
+            _speedsByType.TryGetValue(bc.GetType(), out sp))
+        {
+            activeSpeed = sp.ActiveSpeed;
+            passiveSpeed = sp.PassiveSpeed;
+            return;
+        }
+
+        // "Fast"
+        activeSpeed = 0.2;
+        passiveSpeed = 0.4;
+    }
+
+    public static void RegisterSpeed(SpeedClassEntry entry)
+    {
+        _speedsByName[entry.Name] = entry;
+
+        foreach (var type in entry.Types)
+        {
+            _speedsByType[type] = entry;
+        }
+    }
+
+    public static void Configure()
+    {
+        ScaleSpeedByDex = ServerConfiguration.GetSetting("movement.delay.scaleSpeedByDex", Core.HS);
+        MinDelay = ServerConfiguration.GetSetting("movement.delay.npcMinDelay", 0.1);
+        MaxDelay = ServerConfiguration.GetSetting("movement.delay.npcMaxDelay", 0.4);
+        MaxDex = ServerConfiguration.GetSetting("movement.delay.npcMinDex", 50);
+        MaxDex = ServerConfiguration.GetSetting("movement.delay.npcMaxDex", 200);
+        MinIdleSeconds = ServerConfiguration.GetSetting("movement.delay.npcMinIdle", 15);
+        MaxIdleSeconds = ServerConfiguration.GetSetting("movement.delay.npcMaxIdle", 25);
+
+        var path = Path.Combine(Core.BaseDirectory, _tablePath);
+        if (!File.Exists(path))
+        {
+            return;
+        }
+
+        var speeds = JsonConfig.Deserialize<SpeedClassEntry[]>(path);
+
+        for (var i = 0; i < speeds.Length; i++)
+        {
+            RegisterSpeed(speeds[i]);
+        }
+    }
+
+    public record SpeedClassEntry
+    {
+        [JsonPropertyName("name")]
+        public string Name { get; init; }
+
+        [JsonPropertyName("active")]
+        public double ActiveSpeed { get; init; }
+
+        [JsonPropertyName("passive")]
+        public double PassiveSpeed { get; init; }
+
+        [JsonPropertyName("types")]
+        public HashSet<Type> Types { get; init; }
+    }
+}