NVDEC (H264): Use separate contexts per channel and decode frames in DTS order (#2671)

* Use separate NVDEC contexts per channel (for FFMPEG)

* Remove NVDEC -> VIC frame override hack

* Add missing bottom_field_pic_order_in_frame_present_flag

* Make FFMPEG logging static

* nit: Remove empty lines

* New FFMPEG decoding approach -- call h264_decode_frame directly, trim surface cache to reduce memory usage

* Fix case

* Silence warnings

* PR feedback

* Per-decoder rather than per-codec ownership of surfaces on the cache

Ryujinx.Graphics.Device/IDeviceStateWithContext.cs

@@ -0,0 +1,9 @@
+namespace Ryujinx.Graphics.Device
+{
+    public interface IDeviceStateWithContext : IDeviceState
+    {
+        long CreateContext();
+        void DestroyContext(long id);
+        void BindContext(long id);
+    }
+}