Support for running in rootless containers

Description

AnCIble fails in some runners: details at tpo/tpa/team#42038 (closed) (this comment in special).

While some progress has been made by building a custom container, AnCIble still requires rootful CI runners.

Tasks

• Make AnCIble run in rootless containers.
• Remove the restriction on running jobs only on certain runners.
• Optionally remove the tests/ci-runners branch if CI succeeds.
• Cleanup CI configuration, including:
  • Check whether runc and runsc need to be explicitly installed.
  • Remove references for running podman with sudo.