GStreamerMediaPlayer: accept full GstBin descriptions in "audioSink"

Rather than only accept a sink element type in SampleApp config's
gstreamerMediaPlayer -> audioSink setting (like "alsasink" or
"pulsesink"), let the user specify the name plus any parameters and
even multiple subelements to go at the end of the pipeline if needed.
The following is a useful example:

"audioSink":"pulsesink stream-properties=\"props,media.role=announce\""

in combination with the pulseaudio "module-role-ducking" module to
enable attenuating music and other audio during Alexa announcements.

Author: balrog-kun

MediaPlayer/GStreamerMediaPlayer/src/MediaPlayer.cpp

@@ -677,26 +677,34 @@ bool MediaPlayer::setupPipeline() {
         }
     }
 
-    std::string audioSinkElement;
+    std::string audioSinkDescription;
     ConfigurationNode::getRoot()[MEDIAPLAYER_CONFIGURATION_ROOT_KEY].getString(
-        MEDIAPLAYER_AUDIO_SINK_KEY, &audioSinkElement, "autoaudiosink");
-    m_pipeline.audioSink = gst_element_factory_make(audioSinkElement.c_str(), "audio_sink");
-
-    /// If the sink is a fakesink, set sync to true so that it uses system clock for consuming the buffer
-    /// instead of the default behavior, which is to consume the buffer as fast as possible.
-    if (audioSinkElement == "fakesink") {
-        m_isFakeSink = true;
-        g_object_set(m_pipeline.audioSink, "sync", true, NULL);
-    }
+        MEDIAPLAYER_AUDIO_SINK_KEY, &audioSinkDescription, "autoaudiosink");
+    GError* error = NULL;
+    m_pipeline.audioSink = gst_parse_bin_from_description_full(
+        audioSinkDescription.c_str(),
+        TRUE,
+        NULL,
+        static_cast<GstParseFlags>(GST_PARSE_FLAG_FATAL_ERRORS | GST_PARSE_FLAG_NO_SINGLE_ELEMENT_BINS),
+        &error);
 
     if (!m_pipeline.audioSink) {
         ACSDK_ERROR(LX("setupPipelineFailed")
                         .d("name", RequiresShutdown::name())
                         .d("reason", "createAudioSinkElementFailed")
-                        .d("audioSinkElement", audioSinkElement));
+                        .d("errorMessage", error->message)
+                        .d("audioSinkDescription", audioSinkDescription));
+        g_error_free(error);
         return false;
     }
 
+    /// If the sink is a fakesink, set sync to true so that it uses system clock for consuming the buffer
+    /// instead of the default behavior, which is to consume the buffer as fast as possible.
+    if (audioSinkDescription == "fakesink") {
+        m_isFakeSink = true;
+        g_object_set(m_pipeline.audioSink, "sync", true, NULL);
+    }
+
     GstCaps* caps = gst_caps_new_empty_simple("audio/x-raw");
     if (!caps) {
         ACSDK_ERROR(