Separate domain mapping from uptime checks

This module only enables uptime checks if var.dns_name is not blank. For services behind load balancers this is sub-optimal since var.dns_name will not be set but we still would like uptime checks.

Re-factor the monitoring module from this module into a stand-alone servicemonitoring project hosted in the infra/terraform/ namespace on GitLab which can also be used by load balanced services.