cdc: support top-level compression option for kafka

[techcodie]

Description

The kafka sink historically supported the "Compression" option inside the kafka_sink_config JSON object, but rejected compression as a top-level option. This created inconsistency and confusion, as documented in #113495.

This commit allows using the compression top-level option with the kafka sink. It reads the top-level option (if present) and applies the correct codec to the sarama configuration, making it align with how other sinks receive compression settings.

Fixes #113495

Release Notes

• changefeedccl: improved the kafka sink to accept the top-level compression option in CREATE CHANGEFEED statements, alongside the kafka_sink_config option.

[trunk-io]

Merging to master in this repository is managed by Trunk.

• To merge this pull request, check the box to the left or comment /trunk merge below.

[blathers-crl]

Thank you for contributing to CockroachDB. Please ensure you have followed the guidelines for creating a PR.

Before a member of our team reviews your PR, I have some potential action items for you:

• Please ensure your git commit message contains a release note.
• When CI has completed, please ensure no errors have appeared.

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[cockroach-teamcity]

This change is 

[blathers-crl]

Thank you for updating your pull request.

Before a member of our team reviews your PR, I have some potential action items for you:

• We notice you have more than one commit in your PR. We try break logical changes into separate commits, but commits such as "fix typo" or "address review commits" should be squashed into one commit and pushed with --force
• Please ensure your git commit message contains a release note.
• When CI has completed, please ensure no errors have appeared.

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[blathers-crl]

Thank you for updating your pull request.

Before a member of our team reviews your PR, I have some potential action items for you:

• We notice you have more than one commit in your PR. We try break logical changes into separate commits, but commits such as "fix typo" or "address review commits" should be squashed into one commit and pushed with --force
• Please ensure your git commit message contains a release note.
• When CI has completed, please ensure no errors have appeared.

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[blathers-crl]

Thank you for updating your pull request.

Before a member of our team reviews your PR, I have some potential action items for you:

• We notice you have more than one commit in your PR. We try break logical changes into separate commits, but commits such as "fix typo" or "address review commits" should be squashed into one commit and pushed with --force
• Please ensure your git commit message contains a release note.
• When CI has completed, please ensure no errors have appeared.

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[techcodie]

Thanks for the review! I've updated both the v1 (sarama) and v2 (kgo) paths to include a comment clarifying that if both the top-level compression option and the Producer.Compression in kafka_sink_config are set, the top-level option takes precedence.

This keeps the behavior consistent with how other sinks prioritize top-level options over sink-specific JSON configurations. I also fixed the buildKafkaConfig signature in the v1 path which was previously referencing sinkOpts without it being in the parameter list. The updated commit has been pushed to the branch.