mm: Migrate service in Horizon project (#5580)

* mm: Migrate service in Horizon project

This PR migrate the `mm:u` service to the Horizon project, things were checked by some RE aswell, that's why some vars are renamed, the logic should be the same as before.

Tests are welcome.

* Lock _sessionList instead

* Fix comment

* Fix Session fields order

src/Ryujinx.Horizon/MmNv/MmNvMain.cs

@@ -0,0 +1,17 @@
+namespace Ryujinx.Horizon.MmNv
+{
+    class MmNvMain : IService
+    {
+        public static void Main(ServiceTable serviceTable)
+        {
+            MmNvIpcServer ipcServer = new();
+
+            ipcServer.Initialize();
+
+            serviceTable.SignalServiceReady();
+
+            ipcServer.ServiceRequests();
+            ipcServer.Shutdown();
+        }
+    }
+}