Use a custom podman image for CI

Description

AnCIble is relying on the podman base image, but running jobs as root in order to install packages and change the configuration, which is sub-optimal and fails in some runners: details at tpo/tpa/team#42038 (closed) (this comment in special)

Tasks

• Build a custom podman image on CI, with all the need dependencies. Take this example as a starting point.
• Update jobs to run under the regular podman user.
• Remove the restriction on running jobs only on certain runners. Moved to #6.
• Optionally remove the tests/ci-runners branch if CI succeeds.
• Create a pipeline schedule for this project. Moved to #6.
• Cleanup CI configuration, including:
  • Check whether runc and runsc need to be explicitly installed. Moved to #6.
  • Remove references for running podman with sudo. Moved to #6.

Time estimation

• Complexity: medium (3 days)
• Uncertainty: high (x2)
• Reference (adapted)