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/Sdk/MmNv/Module.cs

@@ -0,0 +1,15 @@
+namespace Ryujinx.Horizon.Sdk.MmNv
+{
+    enum Module : uint
+    {
+        Cpu,
+        Gpu,
+        Emc,
+        SysBus,
+        MSelect,
+        NvDec,
+        NvEnc,
+        NvJpg,
+        Test,
+    }
+}