The switch to not use system packages for containerd packages happened
multiples releases ago ; there should not be any up-to-date installation
of kubespray needing that cleanup.
Remove those steps and variables only used by them.
* Containerd: download containerd from upstream instead of using distro specific packages
split runc download to separate role
make bootstrap-os role deploy container-selinux and seccomp libraries
clean up package manager provided containerd
move variables to docker role that are no longer common with containerd
* Containerd: make molecule testing more relevant
* replace ubuntu18 with ubuntu20
* add centos8 and debian11 to molecule tests
* run kubernetes/preinstall role to ensure relevancy
of test including dependency packages
* CI: adjust test scenarios for downloaded containerd
