Implement HwOpus multistream functions (#3275)

* Implement HwOpus multistream functions

* Avoid one copy

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

@@ -0,0 +1,11 @@
+namespace Ryujinx.HLE.HOS.Services.Audio.HardwareOpusDecoderManager
+{
+    interface IDecoder
+    {
+        int SampleRate { get; }
+        int ChannelsCount { get; }
+
+        int Decode(byte[] inData, int inDataOffset, int len, short[] outPcm, int outPcmOffset, int frameSize);
+        void ResetState();
+    }
+}