fix: Fixes assembly loading. (#759)

* `AssemblyHandler.Assemblies` will now only contain assemblies listed in `assemblies.json`
* `assemblies.json` has been updated to only contain asssemblies directly loaded by the server. Namely, only `UOContent.dll`.
  * Specifically assemblies loaded by assemblies.json are subject to check for `Configure` and `Initialize` methods.
* `modernuo.json` now has a new property called `assemblyDirectories`. This will be automatically set to `Distribution/Assemblies` (absolute path on your machine).
  * You can add more directories to this list.
* All assemblies in assemblies.json _AND_ dependents of any assembly will be searched for in the directories specified by `assemblyDirectories`.

Projects/Server/Configuration/ServerSettings.cs

@@ -21,6 +21,9 @@ namespace Server
 {
     public class ServerSettings
     {
+        [JsonPropertyName("assemblyDirectories")]
+        public List<string> AssemblyDirectories { get; set; } = new();
+
         [JsonPropertyName("dataDirectories")]
         public List<string> DataDirectories { get; set; } = new();