Bump backbeat for hashed oplog ingestion

[delthas]

This bumps backbeat and moves to the new hashed oplog ingestion (that listens to all buckets). See https://github.com/scality/citadel/pull/375 scality/backbeat#2869

• We also force the number of connectors to be 2 (instead of the default 1) such that we properly test behavior with multiple connectors in our e2e tests (avoiding hiding issues that would only show up on >1 connectors) (as was discussed on the design)
• A big chunk of Kafka Connect code is removed because we don't need to wait for the bucket to be listened on: everything is always listened to all the time, that's the point!

Issue: ZENKO-5375

[bert-e]

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[claude]

Backbeat points at a personal playground registry and a dev build tag, not a released tag on ghcr.io/scality. This must be reverted to ghcr.io/scality with the released BB-906 tag before merge, otherwise release packaging pulls an unpublished image.

[delthas]

I know

[bert-e]

Waiting for approval

The following approvals are needed before I can proceed with the merge:

• the author

• 2 peers