LibAudio: Fixed stuttery playback of audio

When playing an ABuffer, the count of samples were determined by the
size of the SharedBuffer. This caused small pauses of up to 512
samples during the playback, when the size of the shared buffer was
rounded up to a multiple of 4096. This problem was amplified by the
fact that the AResampleHelper was created every time a new chunk of
audio was to be processed, causing inconsistencies in the playback of
wav files.

Libraries/LibAudio/AWavLoader.h

@@ -4,6 +4,7 @@
 #include <AK/RefPtr.h>
 #include <AK/StringView.h>
 #include <LibCore/CFile.h>
+#include <LibAudio/ABuffer.h>
 
 class ABuffer;
 
@@ -31,6 +32,7 @@ private:
     bool parse_header();
     RefPtr<CFile> m_file;
     String m_error_string;
+    OwnPtr<AResampleHelper> m_resampler;
 
     u32 m_sample_rate { 0 };
     u16 m_num_channels { 0 };