release-25.4: changefeedccl: add context cancel check to kafkav1

[rharding6373]

Backport 1/1 commits from #162058 on behalf of @rharding6373.

---

Added a missing context check to handleBufferedRetries.

Epic: none
Fixes: #131223

Release note (bug fix): Fixes a bug in kafka v1 where a changefeed could potentially hang if the changefeed was shutting down.

---

Release justification: Low-risk change to fix a potential hang in a deprecated feature.

[blathers-crl]

Thanks for opening a backport.

Before merging, please confirm that it falls into one of the following categories (select one):

• Non-production code changes. Includes test-only changes, build system changes, etc.
• Fixes for serious issues. Defined in the policy as correctness, stability, or security issues, data corruption/loss, significant performance regressions, breaking working and widely used functionality, or an inability to detect and debug production issues.
• Other approved changes. These changes must be gated behind a disabled-by-default feature flag unless there is a strong justification not to.

Add a brief release justification to the PR description explaining your selection.

Also, confirm that the change does not break backward compatibility and complies with all aspects of the backport policy.

All backports must be reviewed by the TL and EM for the owning area.

[trunk-io]

Merging to release-25.4 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]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

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

[blathers-crl]

❌ PR #162120 does not comply with backport policy

Confidence: high
Explanation: The pull request introduces changes in the pkg/ccl/changefeedccl/sink_kafka.go file which is a production file. According to the policy, unless the change fixes a critical bug or is gated behind a disabled feature flag, it does not meet the requirement for backport compliance. While the PR body mentions a low-risk change to address a potential hang condition in Kafka v1, the modification does not clearly satisfy any of the listed critical bug criteria without further evidence of its impact on stability or performance. There is no reference to a feature flag introduction or use, and the release justification itself indicates the update is for a deprecated feature, questioning the critical nature of the bug.
Recommendation: Reconsider the backport as it doesn't clearly meet the critical bug criteria or feature flag requirements for release-25.4, or provide additional justification or evidence indicating the critical impact of this bug.

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

[cockroach-teamcity]

This change is