flaky kokoro required tests blocking PRs

- https://btx.cloud.google.com/invocations/34499825-1183-4aed-8036-669e4ab85ff4/targets/cloud-devrel%2Fclient-libraries%2Fjava%2Fgoogle-cloud-java%2Fpresubmit%2Fdatastore-integration/details
- https://btx.cloud.google.com/invocations/40bedb3d-7df1-4c39-9b2b-027d93673bef/targets/cloud-devrel%2Fclient-libraries%2Fjava%2Fgoogle-cloud-java%2Fpresubmit%2Flogging-integration/details
- https://btx.cloud.google.com/invocations/81fd67b2-2c52-4fb9-bc94-1e60ffb409b3/targets/cloud-devrel%2Fclient-libraries%2Fjava%2Fgoogle-cloud-java%2Fpresubmit%2Fspanner-integration/details

Start with the three linked Kokoro invocation details for the datastore, logging, and spanner integration presubmit targets. Compare the reported failures and the corresponding integration-test runs to determine whether the tests are flaky. Done means the required presubmit tests no longer block healthy pull requests, with the relevant failure evidence and verification recorded.

Vom Indexierungsmodell aus dem Issue-Text verfasst.