feat(connector): Add Cassandra sink connector

### Description

I'd like to add a Cassandra sink connector.

It's on the connector roadmap (#2753) as Sink, P2, with `scylla` as the suggested crate.

There's no wide-column sink today. The 13 existing sinks cover analytical and lakehouse.

The roadmap also lists ScyllaDB as its own row (P3), annotated as covered by the Cassandra connector and pointing at the same crate. `scylla` is pure Rust and Cassandra-compatible, so one implementation should close both rows.

The workloads the roadmap cites for Cassandra - high-write wide-column, time-series and IoT at scale are stream-fed by nature. Devices at that volume don't write to Cassandra directly, they publish to a broker and something drains the stream into the table, with buffering and replay in between. That's the gap this fills.

### Affected area / component

Connectors

### Proposed solution

_No response_

### Alternatives considered

_No response_

### Contribution

- [x] I'm willing to submit a pull request to implement this feature

### Good first issue

- [ ] I think this could be a good first issue for a new contributor