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/ChClassId.cs

@@ -0,0 +1,20 @@
+namespace Ryujinx.Graphics
+{
+    enum ChClassId
+    {
+        Host1x              = 0x1,
+        VideoEncodeMpeg     = 0x20,
+        VideoEncodeNvEnc    = 0x21,
+        VideoStreamingVi    = 0x30,
+        VideoStreamingIsp   = 0x32,
+        VideoStreamingIspB  = 0x34,
+        VideoStreamingViI2c = 0x36,
+        GraphicsVic         = 0x5d,
+        Graphics3d          = 0x60,
+        GraphicsGpu         = 0x61,
+        Tsec                = 0xe0,
+        TsecB               = 0xe1,
+        NvJpg               = 0xc0,
+        NvDec               = 0xf0
+    }
+}