Support and test "re-imageable" compute nodes via compute node metadata

[bertiethorpe]

Support and test "re-imageable" compute nodes:

• Add functionality to skeleton TF to allow defining enable_ flags in compute node metadata, as a list of roles/functionalities to enable.
• Set the enable_* metadata in stackhpc environment only to turn on compute, etc_hosts, nfs, basic_users, eessi. This is all currently supported functionality except for resolv_conf (not used in stackhpc), manila (not available at either leafcloud or sms)
• Add steps to stackhpc workflow, after sucessful reimage of control/login nodes, to reimage compute nodes (with same image) via ansible adhoc, and to check that nodes come back successfully.
• Document the supported metadata flags
• Document the above reimaging workflow

[sjpb]

Need to make it so compute_init_enable can be set differently on different compute groups.

Doing git diff HEAD...main on this branch shows the images are out of date with the current main. So it needs to be updated from main.

[bertiethorpe]

fat image build: https://github.com/stackhpc/ansible-slurm-appliance/actions/runs/12698399333

[sjpb]

One query