The commit allows the maintainer / owner to configure
their preferred GCP region per environment from the
`Project :: Infra :: Google Cloud` section

Change list:
* Backend:
    * Update the `infrastructure_menu` to recognize `:gcp_regions`as an active route for `:google_cloud`
    * `routes/google_cloud` includes the `gcp_regions_controller` routers
    * `gcp_regions_controller` with implementations for showing form and processing form submit
    * `gcp_regions_service` to list out GCP region vars for project
    * `gcp_regions_finder` lists regions for a given project
* Frontend
    * `gcp_regions_list` component to list out regions configured for project
    * `home` includes `gcp_regions_list`
    * `gcp_regions_form` can be used to configure a new region / env mapping
    * template for `gcp_regions_form`
    * `app` recognizes `GCP_REGIONS_FORM` screen