[Feature request] Expose complete MQTT publish context to PayloadFormatter

### Search before asking

- [x] I searched in the [issues](https://github.com/apache/iotdb/issues) and found nothing similar.

### Motivation

Currently, the MQTT `PayloadFormatter` interface receives only the topic and payload.

For custom MQTT ingestion scenarios, it would be helpful if `PayloadFormatter` could also access additional MQTT publish metadata, such as:

- client ID
- username
- QoS
- topic
- payload

In particular, access to `clientId` is useful when the MQTT connection identity needs to be preserved as part of the stored data.

It would therefore be helpful if the formatter API could expose the complete MQTT publish context rather than only `topic` and `payload`.

Backward compatibility with existing custom `PayloadFormatter` implementations would also be appreciated.

Thank you for considering this enhancement.

### Solution

_No response_

### Alternatives

_No response_

### Are you willing to submit a PR?

- [ ] I'm willing to submit a PR!

Locate the MQTT PayloadFormatter interface and its existing implementations, then trace how MQTT publish topic and payload reach the formatter. Determine how the complete publish context and backward compatibility should be represented; done means custom formatters can access the requested metadata without breaking existing implementations.

Scritto dal modello di indicizzazione a partire dal testo della issue.