Add variable to not use Red Hat subscription

[nesies]

Code of Conduct

• I have read and agree to the project's Code of Conduct.

Description

Red Hat subscription is mandatory in kickstart and playbook.
But someboy (me) might want to not use subscription.

Use Case(s)

a Red Hat without subscription

Potential Configuration

add a variable +rhsm_enabled_ in builds/rhsm.pkrvars.hcl.example_
And use it in packer / playbook

References

No response