Mixer needs to scale better given the growing number of bundles in Clear

[gtkramer]

As of one month ago for 27760, mixer build bundles took 19 minutes or so. Today, mixer build bundles for 28350 takes 41 minutes or so. Given we've more than doubled content in the distro, we've seen roughly linear growth. However, we've also come to better understand the overhead of using mixer. For comparison, doing just a dnf install of all bundles manually for the same build one month ago took around 11 minutes and today takes around 19 minutes. This is to start and track a discussion around what can be done to help DevOps to continue iterating quickly.

One possible piece to the solution could be to remove all duplicate provides for our RPM repository. This would make our RPM repository deterministic so that dnf would never need to pick one package over another. Then a single dnf install could be performed by mixer to create the chroot rather than 843.

As suggested by @bryteise, there may be ways to parse the repodata directly rather than relying on dnf to reduce metadata gathering times.

[gtkramer]

Closing, obsoleted by #630