Refactor starter and simplify deployments

[davesee]

Organize into platform and app config folders.
Standardize folder names and *.tfstate file names to match.
Ensure deployments are simple and can be deployed in a reasonable timeframe.

[cedrox]

I see that the sandpit with pipelines doesn't reflect the new folder structure of caf-terraform-landingzones.
My recent try on 2106 + starter branch of the caf-terraform-landingzones-starter don't work from on devops. Pipeline reference folder like caf_foundations or caf_shared_services

Thanks