Part of #8128, followed by #8502.
## Problem
Currently we lack mechanism to alert unhealthy `scan_metadata` status if
we start running this scrubber command as part of a cronjob. With the
storage controller client introduced to storage scrubber in #8196, it is
viable to set up alert by storing health status in the storage
controller database.
We intentionally do not store the full output to the database as the
json blobs potentially makes the table really huge. Instead, only a
health status and a timestamp recording the last time metadata health
status is posted on a tenant shard.
Signed-off-by: Yuchen Liang <yuchen@neon.tech>
The binary etc were renamed some time ago, but the path in the source
tree remained "attachment_service" to avoid disruption to ongoing PRs.
There aren't any big PRs out right now, so it's a good time to cut over.
- Rename `attachment_service` to `storage_controller`
- Move it to the top level for symmetry with `storage_broker` & to avoid
mixing the non-prod neon_local stuff (`control_plane/`) with the storage
controller which is a production component.
