fix: Use KafkaWriter in dataobj-tee

[grobinson-grafana]

What this PR does / why we need it:

This commit uses the KafkaWriter in the dataobj-tee so both topics use the same limits in pkg/kafka/client/writer_client.go.

In future, we will deprecate the limits from writer_client.go and use MaxBufferedBytes instead, since twmb/franz-go/issues/777 has been fixed.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR

---

Note

Medium Risk
Touches the distributor write path to Kafka by changing the producer type and ProduceSync call signature; behavior should be equivalent but miswiring could break or alter tee writes under load.

Overview
The data-object tee now writes via the distributor’s shared KafkaProducer (kafkaWriter) instead of using a dedicated *kgo.Client, so both Kafka topics follow the same writer limits/configuration.

This updates DataObjTee/NewDataObjTee to accept KafkaProducer and adjusts the ProduceSync invocation to match the producer API.

^{Reviewed by Cursor Bugbot for commit 6dfdc5c. Bugbot is set up for automated code reviews on this repo. Configure here.}