Administrator controls for cloud mirrors

[bemoody]

Project cloud mirrors (GCP and AWS buckets) are created via the published project management page (https://physionet.org/console/published-projects/mitdb/1.0.0/)

Some additional controls that should be available to storage administrators:

• Buttons to temporarily enable/disable access to the cloud mirror.
• Buttons to temporarily show/hide the cloud mirror from the published project page.
• A button to disable all access and delete the cloud mirror.

These will require adding fields to the GCP and AWS models to indicate whether the mirror is "visible" and/or "accessible".

We will also need to implement:

• Disabling access to public GCP buckets: probably this just means toggling the bucket to "private".
• Disabling access to controlled GCP buckets: probably we want to leave the fake email list as-is, but remove its access privileges.
• Disabling access to AWS prefixes: probably we want to add a "deny" policy rule to the bucket. Note that this means there is an upper limit on the number of disabled projects.