This adds the initial nodepool-in-zuul config to:
* Tell zuul that it's responsible for an image named "debian-bullseye"
* Attach the job to a pipeline that builds missing images
* Connect to raxflex and upload that image
* Use that image when launching nodes with a label of
"niz-debian-bullseye-normal"
Change-Id: I8a838253a4683f34f538c90949369ba2d192e8d7
5a14ae734d