Add openeuler-minimal element and add CI functional tests for both
x86_64 and arm64.
OpenEuler is an open source community driven YUM/DNF distro like
Fedora. It references Fedora and CentOS a lot for the rpm packages
building. So somewhat it can be treated as a redhat family distro
and reuse the YUM/DNF related elements to help build openEuler images.
For more info about openEuler, see: https://openeuler.org/en
Depends-On: https://review.opendev.org/c/zuul/zuul-jobs/+/803413
Change-Id: I3e06e49b524364c3a4edeba8bce7a8c06b9c7b76
