Added Rocky 9 and Ubuntu 22 to test suite.
Dropped CentOS 6.
Changed default OS for tests from CentOS 7 to Rocky 9.
Adapted to using podman for the test suite.
Reduced minimum disk space requirement for testing
from 1G to 10M.
To be revisited:
* Disabled OOM killer defenese feature and systemd due to
compatibility issues with the test environment.
* Disabled systemd by moving systemctl aside
Enhanced build_docker_image.sh; added '-clean' option and added
support for more platforms.
Updated OS-specific packages as needed for all platforms, e.g.
adding 'file' and 'rsync' utils as needed in Docker definitions.
Added minimum performance recommendations for test containers in
config.
Updated env.sh utilities.
This change test on:
[X] centos7
[X] rocky8
[X] rocky9
[X] ubuntu20
[X] ubuntu22
TO DO:
* This builds using the official SDP test suite run manually on
Tom's laptop. Next step: Get it working on our shiny new Jenkins
Rocky 9 server machine.