Implement HwOpus multistream functions (#3275)

* Implement HwOpus multistream functions

* Avoid one copy

Ryujinx.HLE/HOS/Services/Audio/HardwareOpusDecoderManager/Decoder.cs

@@ -0,0 +1,27 @@
+using Concentus.Structs;
+
+namespace Ryujinx.HLE.HOS.Services.Audio.HardwareOpusDecoderManager
+{
+    class Decoder : IDecoder
+    {
+        private readonly OpusDecoder _decoder;
+
+        public int SampleRate => _decoder.SampleRate;
+        public int ChannelsCount => _decoder.NumChannels;
+
+        public Decoder(int sampleRate, int channelsCount)
+        {
+            _decoder = new OpusDecoder(sampleRate, channelsCount);
+        }
+
+        public int Decode(byte[] inData, int inDataOffset, int len, short[] outPcm, int outPcmOffset, int frameSize)
+        {
+            return _decoder.Decode(inData, inDataOffset, len, outPcm, outPcmOffset, frameSize);
+        }
+
+        public void ResetState()
+        {
+            _decoder.ResetState();
+        }
+    }
+}