Add inventory hostname label support

[Yonas-Dresen]

SUMMARY

Fixes #463 Add labels option to the hostname section of the gcp inventory

ISSUE TYPE

• Feature Pull Request

COMPONENT NAME

gcp_compute

ADDITIONAL INFORMATION

If the supplied label exists the inventory_hostname will be the label value. This feature is already available in the AWS and Azure inventory. This would lift the need to rename virtual machines. You can now rename the inventory name by changing a tag. The real VM name can be an ID while the user can interact with something more human-friendly.

hostnames:
  - labels.vm_name
  - public_ip
  - private_ip
  - name