release-25.1: kvcoord: add logging in TestWaiterOnRejectedCommit

[blathers-crl]

Backport 1/1 commits from #148917 on behalf of @pav-kv.

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This should help debugging/deflaking this test should it fail again. The conjecture is that we end up with more than one command ID, and only one gets the injected error, while another one succeeds.

Informs #148910

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Release justification: test-only logging

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
• Backports should not break backwards-compatibility.
• Backports should change as little code as possible.
• Backports should not change on-disk formats or node communication protocols.
• Backports should not add new functionality (except as defined
  here).
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  policy.

If your backport adds new functionality, please ensure that the following additional criteria are satisfied:

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
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[cockroach-teamcity]

This change is 

[blathers-crl]

✅ PR #148950 is compliant with backport policy

Confidence: high
Backward compatible: true
Explanation: This pull request complies with the CockroachDB backport policy for non-production changes. The changes are made in a file designated for testing (pkg/kv/kvclient/kvcoord/integration_test.go). Moreover, the file name fits the pattern of non-production files (*_test.go) which classifies it specifically as a test-only file. Additionally, the PR body includes a valid 'Release justification' that clearly states the changes are exclusively for enhancing test logging and for debugging purposes. Given that the changes are limited to a testing file and have a clear non-production scope, they do not require feature flag gating or a critical bug fix. Additionally, there is no backward compatibility issue as this is a test-only change.

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