WIP: Support gcloud image creation with packer

What does this Merge Request do?

Adds support for creating gcloud images with the GDK environment setup, so that a user can quickly create cloud vm instances to run GDK with minimum setup.

What is setup out of the box and works:

• object store
• container registry
• runners
• elastic search

What requires post install steps:

• installing ssh keys
• configuring NGINX keys
• seeding the license
• indexing elastic search

Things to improve:

• How to make a smooth transition between the logged user and the gdk user, to avoid installing ssh keys?
• Better setup the shell with zsh
• Have a better greeting messge upon login
• Instructions for using vscode
• Add some auto shutdown mechanism to prevent the user from forgetting to shutdown the instance. (These instances are expensive as GDK is power hungry, so it's better to keep it on just the amount that you need (ex: at 8h at a time during your work shift).
• update nginx.conf to support https

Merge Request checklist

• Tests added for new functionality. If not, please raise Issue to follow-up.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.

Closes #934 (closed)