Improve metadata scanning a bit
Summary:
Avoid multiple lookups of keys in the metadata map.
Instead, iterate over it and add it to the track.
Saves about 5% in the benchmark.
Depends on D22590
Reviewers: mgallien, ngraham
Reviewed By: ngraham
Tags: Elisa
Differential Revision: https://phabricator.kde.org/D22591