Get genre metadata for Tidal, Qobuz and Spotify

Extract genre information when fetching favorites and search results.
Genre is now populated in the collection and playlists for
tracks from these streaming services.

src/qobuz/qobuzrequest.h

@@ -65,6 +65,7 @@ class QobuzRequest : public QobuzBaseRequest {
     QString album;
     QUrl cover_url;
     bool album_explicit;
+    QString genre;
   };
   struct Request {
     Request() : offset(0), limit(0) {}