Deprecate shared PV/PVCs

[jgwerner]

Deprecate shared directories which are a feature that was implemented at the end of 2020 based on an end-user's specific request. However, in addition to the fact that our other users are not using this feature the architecture on how user's can share directories with one another will change once we move the file system to use an S3-compatible object-store.

[Abhi94N]

Should we have options to use S3 or efs? Especially for local testing, an end user may not have an s3 account

[jgwerner]

@Abhi94N part of the scope of an issue to move entirely away from EFS would be to create storage using something that supports the S3 API, such as Minio.

However in this case we are removing the /shared folder only which is enabled with the shared PV/PVC volumes and mounted to the shared grader Notebooks and optionally the singleuser Notebooks.