Refactoring HOS folder structure (#771)

* Refactoring HOS folder structure

Refactoring HOS folder structure:

- Added some subfolders when needed (Following structure decided in private).
- Added some `Types` folders when needed.
- Little cleanup here and there.
- Add services placeholders for every HOS services (close #766 and #753).

* Remove Types namespaces

Ryujinx.HLE/HOS/Services/Friend/ServiceCreator/NotificationService/NotificationEventHandler.cs

@@ -0,0 +1,83 @@
+using Ryujinx.HLE.Utilities;
+
+namespace Ryujinx.HLE.HOS.Services.Friend.ServiceCreator.NotificationService
+{
+    public sealed class NotificationEventHandler
+    {
+        private static NotificationEventHandler instance;
+        private static object                   instanceLock = new object();
+
+        private INotificationService[] _registry;
+
+        public static NotificationEventHandler Instance
+        {
+            get
+            {
+                lock (instanceLock)
+                {
+                    if (instance == null)
+                    {
+                        instance = new NotificationEventHandler();
+                    }
+
+                    return instance;
+                }
+            }
+        }
+
+        NotificationEventHandler()
+        {
+            _registry = new INotificationService[0x20];
+        }
+
+        internal void RegisterNotificationService(INotificationService service)
+        {
+            // NOTE: in case there isn't space anymore in the registry array, Nintendo doesn't return any errors.
+            for (int i = 0; i < _registry.Length; i++)
+            {
+                if (_registry[i] == null)
+                {
+                    _registry[i] = service;
+                    break;
+                }
+            }
+        }
+
+        internal void UnregisterNotificationService(INotificationService service)
+        {
+            // NOTE: in case there isn't the entry in the registry array, Nintendo doesn't return any errors.
+            for (int i = 0; i < _registry.Length; i++)
+            {
+                if (_registry[i] == service)
+                {
+                    _registry[i] = null;
+                    break;
+                }
+            }
+        }
+
+        // TODO: Use this when we will have enough things to go online.
+        public void SignalFriendListUpdate(UInt128 targetId)
+        {
+            for (int i = 0; i < _registry.Length; i++)
+            {
+                if (_registry[i] != null)
+                {
+                    _registry[i].SignalFriendListUpdate(targetId);
+                }
+            }
+        }
+
+        // TODO: Use this when we will have enough things to go online.
+        public void SignalNewFriendRequest(UInt128 targetId)
+        {
+            for (int i = 0; i < _registry.Length; i++)
+            {
+                if (_registry[i] != null)
+                {
+                    _registry[i].SignalNewFriendRequest(targetId);
+                }
+            }
+        }
+    }
+}

Ryujinx.HLE/HOS/Services/Friend/ServiceCreator/NotificationService/Types/NotificationEventType.cs

@@ -0,0 +1,9 @@
+namespace Ryujinx.HLE.HOS.Services.Friend.ServiceCreator.NotificationService
+{
+    enum NotificationEventType : uint
+    {
+        Invalid          = 0x0,
+        FriendListUpdate = 0x1,
+        NewFriendRequest = 0x65
+    }
+}

Ryujinx.HLE/HOS/Services/Friend/ServiceCreator/NotificationService/Types/NotificationInfo.cs

@@ -0,0 +1,15 @@
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.HLE.HOS.Services.Friend.ServiceCreator.NotificationService
+{
+    [StructLayout(LayoutKind.Sequential, Pack = 0x8, Size = 0x10)]
+    struct NotificationInfo
+    {
+        public NotificationEventType Type;
+
+        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 0x4)]
+        public char[] Padding;
+
+        public long NetworkUserIdPlaceholder;
+    }
+}