Allow node zero ip and ServiceBaseURL to be set by the tui

The node zero ip is currently hard-coded inside set-node-zero.sh.template and in the ServiceBaseURL template string.

ServiceBaseURL is also hard-coded inside:

• apply-host-config.service.template
• create-cluster-and-infraenv-service.template
• common.sh.template
• start-agent.sh.template
• start-cluster-installation.sh.template
• assisted-service.env.template

We need to remove this hard-coding and to allow a user to be able to set the node zero ip through the tui and have it be reflected by the agent services and scripts.