[Chart] Set prom_metrics_display_url automatically

[sotojn]

This PR makes the following changes:

• Adds feature to helm chart template to support dynamic configuration of prom_metrics_display_url
  • If the user explicitly sets prom_metrics_display_url in the terafoundation config, the provided value is used without modification (except making sure a trailing slash is appended if missing). Ex: http://teraslice.local will end up as http://teraslice.local/ in the configmap.
  • When prom_metrics_display_url is not set, the URL is dynamically constructed based on if the ingress.enabled configuration is true or false
    • If true, it will make a url based off of the value in .Values.ingress.hosts.
      • It will also add a https:// prefix if ingress.tls is defined and non-empty. Otherwise will use http:// prefix
    • If false it will leave prom_metrics_display_url unset

Ref to issue #3852

[briend]

Looks good to me. I tested it out with helm template and verified prom_metrics_display_url looked correct for each scenario