Reduce bot difficulty requests (!111)

Requires server-side changes (will need your help @TheSparta for this!).

This combined all the single bot difficulty requests into a single GET request (`/singleplayer/bot/difficulties`) with the following data structure:
```json
[
    {
        "role": "assault",
        "difficulty": "easy",
        "data": "assets/database/bots/types/assault.json difficulty easy contents"
    },
    {
        "role": "pmcbot",
        "difficulty": "normal",
        "data": "assets/database/bots/types/pmcbot.json difficulty normal contents"
    }
]
```
The request expects all roles and all their respective difficulties to be in the response.

Co-authored-by: Merijn Hendriks <merijnhendriks@users.noreply.github.com>
Reviewed-on: SPT-AKI/Modules#111
Reviewed-by: DrakiaXYZ <drakiaxyz@noreply.dev.sp-tarkov.com>
Co-authored-by: Merijn Hendriks <senko-san@noreply.dev.sp-tarkov.com>
Co-committed-by: Merijn Hendriks <senko-san@noreply.dev.sp-tarkov.com>

project/Aki.Custom/Models/DifficultyInfo.cs

@@ -0,0 +1,24 @@
+using System.Runtime.Serialization;
+
+namespace Aki.Custom.Models
+{
+    [DataContract]
+    public struct DifficultyInfo
+    {
+        [DataMember(Name = "role")]
+        public string Role;
+
+        [DataMember(Name = "difficulty")]
+        public string Difficulty;
+
+        [DataMember(Name = "data")]
+        public string Data;
+
+        public DifficultyInfo(string role, string difficulty, string data)
+        {
+            Role = role;
+            Difficulty = difficulty;
+            Data = data;
+        }
+    }
+}

project/Aki.Custom/Patches/BotDifficultyPatch.cs

@@ -1,4 +1,4 @@
-using Aki.Common.Http;
+using Aki.Custom.Utils;
 using Aki.Reflection.Patching;
 using Aki.Reflection.Utils;
 using EFT;
@@ -21,7 +21,7 @@ namespace Aki.Custom.Patches
         [PatchPrefix]
         private static bool PatchPrefix(ref string __result, BotDifficulty botDifficulty, WildSpawnType role)
         {
-            __result = RequestHandler.GetJson($"/singleplayer/settings/bot/difficulty/{role}/{botDifficulty}");
+            __result = DifficultyManager.Get(botDifficulty, role);
             var resultIsNullEmpty = string.IsNullOrWhiteSpace(__result);
             if (resultIsNullEmpty)
             {

project/Aki.Custom/Patches/CoreDifficultyPatch.cs

@@ -2,6 +2,7 @@ using Aki.Reflection.Patching;
 using Aki.Reflection.Utils;
 using Aki.Common.Http;
 using System.Reflection;
+using Aki.Custom.Utils;
 
 namespace Aki.Custom.Patches
 {
@@ -19,6 +20,11 @@ namespace Aki.Custom.Patches
 		[PatchPrefix]
 		private static bool PatchPrefix(ref string __result)
 		{
+			// core difficulty is requested before the others
+			// so update the others now!
+			DifficultyManager.Update();
+
+			// update core difficulty
             __result = RequestHandler.GetJson("/singleplayer/settings/bot/difficulty/core/core");
 			return string.IsNullOrWhiteSpace(__result);
         }

project/Aki.Custom/Utils/DifficultyManager.cs

@@ -0,0 +1,42 @@
+using System.Collections.Generic;
+using EFT;
+using Aki.Common.Http;
+using Aki.Common.Utils;
+using Aki.Custom.Models;
+
+namespace Aki.Custom.Utils
+{
+    public static class DifficultyManager
+    {
+        public static List<DifficultyInfo> Difficulties { get; private set; }
+
+        static DifficultyManager()
+        {
+            Difficulties = new List<DifficultyInfo>();
+        }
+
+        public static void Update()
+        {
+            // remove existing list
+            Difficulties.Clear();
+
+            // get new difficulties
+            var json = RequestHandler.GetJson("/singleplayer/settings/bot/difficulties");
+            Difficulties = Json.Deserialize<List<DifficultyInfo>>(json);
+        }
+
+        public static string Get(BotDifficulty botDifficulty, WildSpawnType role)
+        {
+            foreach (var entry in Difficulties)
+            {
+                if (botDifficulty.ToString().ToLower() == entry.Difficulty
+                && role.ToString().ToLower() == entry.Role)
+                {
+                    return entry.Data;
+                }
+            }
+
+            return string.Empty;
+        }
+    }
+}