k/test: Addition for dry create_topics dry run

[oleiman]

CORE-1274 was fixed by b48d3ac5244b2060f92be4a1ad9dc5e3944f5ef2

This commit adds a unit test.

Backports Required

• [x] none - not a bug fix
• [ ] none - this is a backport
• [ ] none - issue does not exist in previous branches
• [ ] none - papercut/not impactful enough to backport
• [ ] v24.3.x
• [ ] v24.2.x
• [ ] v24.1.x

Release Notes

• none

[vbotbuildovich]

non flaky failures in https://buildkite.com/redpanda/redpanda/builds/58526#0193526c-7e39-4670-843f-2f3b80368151:

"rptest.tests.datalake.coordinator_retention_test.CoordinatorRetentionTest.test_retention.cloud_storage_type=CloudStorageType.S3"

[vbotbuildovich]

Retry command for Build#58526

please wait until all jobs are finished before running the slash command

/ci-repeat 1
tests/rptest/tests/datalake/coordinator_retention_test.py::CoordinatorRetentionTest.test_retention@{"cloud_storage_type":1}

[oleiman]

/ci-repeat 1 skip-redpanda-build skip-units tests/rptest/tests/datalake/coordinator_retention_test.py::CoordinatorRetentionTest.test_retention@{"cloud_storage_type":1}

[oleiman]

CI Failure:

• build - infra failure DEVPROD-2424

[oleiman]

force push merge conflict

[oleiman]

CI Failures:

• ducktape-debug https://redpandadata.atlassian.net/browse/CORE-8278
• bazel test flake

[oleiman]

/ci-repeat 1 skip-redpanda-build skip-units tests/rptest/tests/archive_retention_test.py::CloudArchiveRetentionTest.test_delete