Use Dynamic Normal nodes with 23.02.05-1

[sjpb]

Conflated a few things here:

• This PR changes slurm version to include the minor version and the (presumably, it's not documented, patch level) as well as the major version. This should make builds (more?) repeatable. Note repo branches are only specified as e.g. "slurm-23.02" (major version) but tags are specified as "slurm-23-02-05-1" (major, minor, patch). Note it looks like 23.02.05 makes cloud_reg_addrs the default behavior, although that's not listed in the NEWS/release notes.
• Updates the README to remove mention of the generate secrets script, and some other tweaks/moves to make it easier to follow
• Changes to use Dynamic Normal nodes (i.e. slurmd -Z). This removes need to configure memory/CPU, and appears to work with TreeWidth set and cloud_dns NOT set in slurm.conf