Refactor the friend namespace (#721)

* Refactor the friend namespace and UInt128

This commit also:
- Fix GetFriendsList arguments ordering.
- Add GetFriendListIds.
- Expose the permission level of the port instance.
- InvalidUUID => InvalidArgument

* friend: add all cmds as commments

* add Friend structure layout

* Rename FriendErr to FriendError

* Accurately implement INotificationService

* Fix singleton lock of NotificationEventHandler

* Address comments

* Add comments for IDaemonSuspendSessionService cmds

* Explicitly define the Charset when needed

Also make "Nickname" a string

* Address gdk's comments

Ryujinx.HLE/HOS/Services/Friend/FriendError.cs

@@ -0,0 +1,8 @@
+namespace Ryujinx.HLE.HOS.Services.Friend
+{
+    static class FriendError
+    {
+        public const int InvalidArgument        = 2;
+        public const int NotificationQueueEmpty = 15;
+    }
+}