Add build improvements.

[aditigaur4]

• Move all scripts (such as build scripts) to a util directory
• Use a dockerfile that builds an image for packaging azslurm, so that build environment gets cached locally.
• Make sure slurm_supported_versions.py points to a version that is downloadable schedmd.slurm.com. Because the versions are appended with a "-1", when download url links are created, we create the wrong link and docker_rpmbuild.sh fails.
• make all scripts use podman or docker depending on which is available. Signed-off-by: Aditi Gaur aditigaur@microsoft.com