AudioStream: Replace buffer queue with ring buffer

Should achieve a decent overall minimum latency reduction.

src/core/settings.h

@@ -71,7 +71,6 @@ struct Settings
   AudioBackend audio_backend = AudioBackend::Cubeb;
   s32 audio_output_volume = 100;
   u32 audio_buffer_size = 2048;
-  u32 audio_buffer_count = 4;
   bool audio_output_muted = false;
   bool audio_sync_enabled = true;
   bool audio_dump_on_boot = true;