[CBM] Investigate whether further gains can be made in staging directory performance

We have seen a customer have poor performance populating the staging directory. We should do some more investigation into what takes up the time now that MB-53764 is fixed and see if there are any other easy gains to be made. Thoughts:

1. Concurrent listing of repos
2. Concurrent unzipping
3. Investigate if there is a quicker compression algorithm we could use
4. Is there a better way to tell whether we need to check the files match with the archive?