ldn: Implement calls of UserLocalCommunicationService (#829)

* ldn: Implement calls of UserLocalCommunicationService

- Implement `IUserServiceCreator: CreateUserLocalCommunicationService` according to RE.
- Implement `IUserLocalCommunicationService` calls:
  - Every calls in this interface are layered to `NetworkInterface`.
  - `GetState` according to RE.
  - `InitializeOld`, `Initialize` and `Finalize` stubbed with the appropriate result code and some TODO according to RE.
  - `AttachStateChangeEvent` according to RE.

* Fix var name and TODO comments

* Fix review

Ryujinx.HLE/HOS/Services/Ldn/ResultCode.cs

@@ -0,0 +1,16 @@
+namespace Ryujinx.HLE.HOS.Services.Ldn
+{
+    enum ResultCode
+    {
+        ModuleId       = 203,
+        ErrorCodeShift = 9,
+
+        Success = 0,
+
+        DeviceDisabled  = (22 << ErrorCodeShift) | ModuleId,
+        InvalidState    = (32 << ErrorCodeShift) | ModuleId,
+        Unknown1        = (48 << ErrorCodeShift) | ModuleId,
+        InvalidArgument = (96 << ErrorCodeShift) | ModuleId,
+        InvalidOjbect   = (97 << ErrorCodeShift) | ModuleId,
+    }
+}