[tests] replace fixed tokio::time::sleep workarounds with wait_for_table_ready helper

[fresh-borzoni]

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Description

Several Rust integration tests use a fixed tokio::time::sleep(1-2s) after create_table / create_partitions to wait for bucket leadership (see list_offsets, test_poll_batches, partitioned_table_append_scan) - brittle on slow CI and adds dead time when the cluster is ready sooner. Add wait_for_table_ready(admin, table_path) (and partitione dvariant) to tests/integration/utils.rs that polls list_offsets /list_partition_offsets until success, mirroring the existing wait_for_cluster_ready_with_sasl shape, and replace the sleeps at all call sites.

Willingness to contribute

• I'm willing to submit a PR!

[slfan1989]

@fresh-borzoni Hi, I’d like to take this issue.

My plan is to add a wait_for_table_ready helper, and a partition-aware variant if needed, then use them to replace the fixed sleeps in the Rust integration tests.

Please let me know if this direction looks good. Thanks!

[fresh-borzoni]

@slfan1989 Thank you, this plan sounds reasonable 👍