Support Bring Your Own Key for Object Storage

[regevran]

Scylla should support user's own key for encrypting data at object storage.
Without this key Scylla does not encrypt the data and leave it for the object storage provider (S3 for example) to take care for encryption.
Refs: https://github.com/scylladb/scylla-enterprise/issues/4981

In general, the flow is always the same:
in the media: encrypted with a key for this media.
When transitioned - decryption with the key for this media and encryption with the keys for the transition to media.
For example:
On local disk - encrypted for local disk.
When streamed to S3: decryption with local disk keys and encryption with TLS.
If the user brings its own keys - before the TLS - encryption using the user's keys.
On S3 (not our responsibility, just to complete the picture) - decryption using TLS, encryption using S3's encryption.

[mykaul]

This is not realistic for 2025.1.0.
@regevran - please re-target.