Improve validate_host_names.yaml

We should improve validate_host_names.yaml by making it clearer to match the regex for a valid internet host and then fail.

• Change CHARS to ValidHostnameRegex = "^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\-]*[A-Za-z0-9])$"
• Change the "when" to item is search('{{ ValidHostnameRegex }}')
• Add IP address validation (based on this stackoverflow)

Another thing that can be done is validate the Mac Address as well

We should also probably change the name of validate_host_names.yaml to validate.yaml for generic validations. We could also break them up into individual files. I'm open for suggestions on that front.

Start with tasks/validate_host_names.yaml and vars/main.yml, comparing the current CHARS and when expression with the requested ValidHostnameRegex and search condition. Done means host validation is clearer and also covers IP addresses; confirm whether MAC validation and the validate.yaml split are in scope before changing them.