Public gateway refactor

[jvallexm]

• Renamed module public_gateway
• Module can now create up to 3 public gateways in a single region in one VPC
• Module can now get public gateways from data
• Added functionality to dynamically check if a floating_ip value is an IP address or an ID
• Added additional outputs and cleaned up existing ones. Module will merge both resource and data gateways for all outputs
  • ids - a list of gateway ids
  • ids_by_zone - produces an object that can be used by the refactored subnet module I put in a PR for
  • addresses - provides a list of gateway IP addresses so that users can easily access them
  • addresses_by_zone - provides an object of gateway IP addresses for each zone