Introduces a new variable `firewall_cfg` in the `sap-hana-preconfigure`
playbook to provide more explicit control over the firewalld service.
This new variable allows to 'enable', 'disable', or 'ignore' the
firewall configuration.
The `sap_hana_install` role is updated to delegate the firewall
service management to the preconfigure playbook, avoiding conflicts
and centralizing the configuration.
The documentation has been updated to reflect these changes.