NVDEC implementation using FFmpeg (#443)

* Initial nvdec implementation using FFmpeg

* Fix swapped channels on the video decoder and the G8R8 texture format

* Fix texture samplers not being set properly (regression)

* Rebased

* Remove unused code introduced on the rebase

* Add support for RGBA8 output format on the video image composer

* Correct spacing

* Some fixes for rebase and other tweaks

* Allow size mismatch on frame copy

* Get rid of GetHostAddress calls on VDec

Ryujinx.Graphics/Graphics3d/NvGpuEngineM2mfReg.cs

@@ -0,0 +1,25 @@
+namespace Ryujinx.Graphics.Graphics3d
+{
+    enum NvGpuEngineM2mfReg
+    {
+        SrcAddress = 0x100,
+        DstAddress = 0x102,
+        SrcPitch   = 0x104,
+        DstPitch   = 0x105,
+        XCount     = 0x106,
+        YCount     = 0x107,
+        Swizzle    = 0x1c2,
+        DstBlkDim  = 0x1c3,
+        DstSizeX   = 0x1c4,
+        DstSizeY   = 0x1c5,
+        DstSizeZ   = 0x1c6,
+        DstPosZ    = 0x1c7,
+        DstPosXY   = 0x1c8,
+        SrcBlkDim  = 0x1ca,
+        SrcSizeX   = 0x1cb,
+        SrcSizeY   = 0x1cc,
+        SrcSizeZ   = 0x1cd,
+        SrcPosZ    = 0x1ce,
+        SrcPosXY   = 0x1cf
+    }
+}