[blob] Add CLI option to enable auto-deletion

Summary:
Since introduction of blob cleanup, specifically D9413, blob integration tests are broken (deletion part)
Until we have ENG-4439 implemented,
we need to have option to restore pre-cleanup behavior. This diff adds a CLI option for that.

Depends on D9508

Test Plan:
Tested with aws-cli (awslocal dynamodb scan --table-name blob-service-blobs)

• With the --instant-delete flag set, calling DELETE endpoint on last holder removes blob and holder rows from DDB
• Without the flag, the blob item DB row is marked as unchecked.

Reviewers: michal, varun, jon

Reviewed By: michal

Subscribers: ashoat, tomek, wyilio

Differential Revision: https://phab.comm.dev/D9509