Audio: Use std::deque instead of std::vector for the audio buffer type (StereoBuffer16).

The current code inserts and deletes elements from the beginning of the audio buffer, which is very inefficient in an std::vector.

Profiling was done using VisualStudio2017's Performance Analyzer in Super Mario 3D Land.

Before this change: AudioInterp::Linear had 14.14% of the runtime (inclusive) and most of that time was spent in std::vector's insert implementation.
After this change: AudioInterp::Linear has 0.36% of the runtime (inclusive)

src/audio_core/hle/source.h

@@ -108,7 +108,7 @@ private:
 
         u32 current_sample_number = 0;
         u32 next_sample_number = 0;
-        std::vector<std::array<s16, 2>> current_buffer;
+        AudioInterp::StereoBuffer16 current_buffer;
 
         // buffer_id state