dt/cluster_linking: Wait for topic and partitions

[BenPope]

If the topic is going to be produced to, wait for the partitions, too.

For example, this avoids the KgoVerifier warning:

"More partitions in valid_offsets file than in topic!"

E.g.: https://ci-artifacts.dev.vectorized.cloud/production-devprod/redpanda/75412/019a3a6a-4e02-4342-9b24-7ecdaa64c418/vbuild/ducktape/results/2025-10-31--001/report.html

Backports Required

• 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
• v25.2.x
• v25.1.x
• v24.3.x

Release Notes

• none

[oleiman]

nice one

[vbotbuildovich]

Retry command for Build#75427

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

/ci-repeat 1
tests/rptest/tests/cluster_linking_e2e_test.py::ShadowLinkUpdateBrokersTests.test_update_brokers

[vbotbuildovich]

CI test results

test results on build#75427

test_class	test_method	test_arguments	test_kind	job_url	test_status	passed	reason	test_history
EndToEndCloudTopicsTxTest	test_write	null	integration	https://buildkite.com/redpanda/redpanda/builds/75427#019a3b3a-ef20-4ca8-abe2-b2e355568bfe	FLAKY	17/21	upstream reliability is '92.08472686733556'. current run reliability is '80.95238095238095'. drift is 11.13235 and the allowed drift is set to 50. The test should PASS	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=EndToEndCloudTopicsTxTest&test_method=test_write
ShadowLinkUpdateBrokersTests	test_update_brokers	null	integration	https://buildkite.com/redpanda/redpanda/builds/75427#019a3b32-cdf2-4ed5-a5c1-549ab39f6e85	FAIL	0/21	The test has failed across all retries	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=ShadowLinkUpdateBrokersTests&test_method=test_update_brokers
ShadowLinkUpdateBrokersTests	test_update_brokers	null	integration	https://buildkite.com/redpanda/redpanda/builds/75427#019a3b3a-ef29-4bff-a37a-d150d00a038f	FAIL	0/21	The test has failed across all retries	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=ShadowLinkUpdateBrokersTests&test_method=test_update_brokers
ShadowLinkingReplicationTests	test_replication_timestamps_match	{"source_cluster_spec": {"cluster_type": "redpanda"}, "timestamp_type": "CreateTime"}	integration	https://buildkite.com/redpanda/redpanda/builds/75427#019a3b3a-ef1f-471a-8d0e-0ff16b440f75	FLAKY	20/21	upstream reliability is '95.28487229862476'. current run reliability is '95.23809523809523'. drift is 0.04678 and the allowed drift is set to 50. The test should PASS	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=ShadowLinkingReplicationTests&test_method=test_replication_timestamps_match
DataMigrationsApiTest	test_creating_and_listing_migrations	null	integration	https://buildkite.com/redpanda/redpanda/builds/75427#019a3b32-cdeb-4e5c-b8a2-f59135fbe1d5	FLAKY	16/21	upstream reliability is '96.52406417112299'. current run reliability is '76.19047619047619'. drift is 20.33359 and the allowed drift is set to 50. The test should PASS	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=DataMigrationsApiTest&test_method=test_creating_and_listing_migrations
MountUnmountIcebergTest	test_simple_remount	{"cloud_storage_type": 1}	integration	https://buildkite.com/redpanda/redpanda/builds/75427#019a3b32-cdeb-4e5c-b8a2-f59135fbe1d5	FLAKY	17/21	upstream reliability is '76.45259938837921'. current run reliability is '80.95238095238095'. drift is -4.49978 and the allowed drift is set to 50. The test should PASS	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=MountUnmountIcebergTest&test_method=test_simple_remount