nfp:user: Implement IUser (#714)

* nfp:user: Implement IUser

- Based on RE of sysmod FW 1.0 and 3.0 with help of https://github.com/switchbrew/libnx/ and https://reswitched.github.io/SwIPC/ifaces.html#nn::nfp::detail::IUser
- Accurate implementation of Initialize, AttachActivateEvent, AttachDeactivateEvent, GetState, GetDeviceState, GetNpadId and GetDeviceState.
- Implementation of Finalize and ListDevices (close #638).

* reorder private var

* fix nits

Ryujinx.HLE/HOS/Services/Nfp/State.cs

@@ -1,8 +0,0 @@
-namespace Ryujinx.HLE.HOS.Services.Nfp
-{
-    enum State
-    {
-        NonInitialized = 0,
-        Initialized = 1
-    }
-}