release-23.2: tests: get cdc_bench cursor at least 1s after table creation

[blathers-crl]

Backport 1/1 commits from #138854 on behalf of @rharding6373.

/cc @cockroachdb/release

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Previously, we would get changefeed cursors from the current time after creating a table and before populating it. Due to the time being at a second granularity, it was possible that the cursor could be the same second that the table was created, which would lead to the table not appearing to be created yet.

This change adds a 1s sleep before getting the cursor timestamp, to ensure that we don't encounter this scenario.

Epic: None

Fixes: #137758
Fixes: #135795

Release note: None

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Release justification: Test-only change to reduce flakiness.

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

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  issues or test-only changes.
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[cockroach-teamcity]

This change is