audout: Implement and fix some calls (#1725)

* audout: Implement GetAudioOutBufferCount, GetAudioOutPlayedSampleCount and FlushAudioOutBuffers

This PR implement audout service calls:
- GetAudioOutBufferCount
- GetAudioOutPlayedSampleCount
- FlushAudioOutBuffers

The RE calls just give some hints about no extra checks.
Since we use a totally different implementation because of our backend, I can't do something better for now.

SetAudioOutVolume and GetAudioOutVolume are fixed too by set/get the volume of the current opened track, previous implementation was wrong.

This fix #1133, fix #1258 and fix #1519.

Thanks to @jduncanator for this help during the implementation and all his precious advices.

* Fix some debug leftovers

* Address jD feedback

Ryujinx.Audio/Renderers/OpenAL/OpenALAudioTrack.cs

@@ -11,9 +11,12 @@ namespace Ryujinx.Audio
         public int           SampleRate { get; private set; }
         public ALFormat      Format     { get; private set; }
         public PlaybackState State      { get; set; }
+        public float         Volume     { get; private set; }
 
         public int HardwareChannels { get; }
         public int VirtualChannels { get; }
+        public uint BufferCount => (uint)_buffers.Count;
+        public ulong PlayedSampleCount { get; set; }
 
         private ReleaseCallback _callback;
 
@@ -125,6 +128,34 @@ namespace Ryujinx.Audio
             }
         }
 
+        public bool FlushBuffers()
+        {
+            while (_queuedTagsQueue.TryDequeue(out long tag))
+            {
+                _releasedTagsQueue.Enqueue(tag);
+            }
+
+            _callback();
+
+            foreach (var buffer in _buffers)
+            {
+                AL.DeleteBuffer(buffer.Value);
+            }
+
+            bool heldBuffers = _buffers.Count > 0;
+
+            _buffers.Clear();
+
+            return heldBuffers;
+        }
+
+        public void SetVolume(float volume)
+        {
+            Volume = volume;
+
+            AL.Source(SourceId, ALSourcef.Gain, Volume);
+        }
+
         public void Dispose()
         {
             Dispose(true);