molecule/perforce-sdp-install: make the role idempotent + add group_vars
Idempotence fixes (the molecule idempotence step now passes):
- install.yml: gate the SDP download/unpack include on 'not sdp_installed'
(unarchive is not idempotent; matches the existing cleanup gate).
- users.yml: known_hosts touch preserves timestamps; ssh_config copy uses
force:false so it doesn't fight the 'Add ssh config lines' blockinfile; drop
'force' on the ansibleuser user (it regenerated the SSH key every run).
- Add molecule/default/group_vars/all.yml (perforce_user_password hash; its '$'
sequences cannot live in molecule.yml due to interpolation).
Full 'molecule test' (create/prepare/converge/idempotence/verify/destroy) now
passes on Ubuntu 22.04 and Rocky 9 (native arm64 + aarch64 binaries).