This review adds the first dependency repo file and
dep_repo_* to include dependency repos in repo
setup. This allows tripleo ci testing of dependency
repos under development.
The first dependency jobs - for centos 8 stream -
are added in https://review.rdoproject.org/r/#/c/29219/.
Change-Id: Ica3af2d69e5e1552c6e56e3be45b2af0d83b7f24