Implement a rudimentary applets system (#804)

* Implement Player Select applet

* Initialize the Horizon system reference

* Tidy up namespaces

* Resolve nits

* Resolve nits

* Rename stack to queue

* Implement an applet FIFO

* Remove debugging log

* Log applet creation events

* Reorganise AppletFifo

* More reorganisation

* Final changes

Ryujinx.HLE/HOS/Applets/PlayerSelect/PlayerSelectResult.cs

@@ -0,0 +1,8 @@
+namespace Ryujinx.HLE.HOS.Applets
+{
+    enum PlayerSelectResult : ulong
+    {
+        Success = 0,
+        Failure = 2
+    }
+}