Treat a 404 from BigQuery table and dataset deletes as success

[mxtymoshyk]

BigQueryIO creates temporary tables and datasets and deletes them when it is done. A delete can succeed at BigQuery and still have its work item fail to commit afterwards. The runner then replays that work item, and the replayed delete gets a 404 because the first attempt already removed the resource.

DatasetServiceImpl.deleteTable and deleteDataset passed ALWAYS_RETRY, so that 404 was retried MAX_RPC_RETRIES (9) times with exponential backoff and then rethrown as an IOException. In a streaming job the work item is retried forever and the job cannot drain.

Both methods now pass DONT_RETRY_NOT_FOUND and swallow an item-not-found error, since "the resource is gone" is the outcome the caller asked for. This mirrors how getTable in the same class already handles a 404. Every other status code keeps its existing retry count and failure behaviour.

fixes #24997

Notes for reviewers

• The 404 is only swallowed for the two delete calls. dryRunQuery and patchTableDescription still use ALWAYS_RETRY, and no getX/create/patch path changed.
• ApiErrorExtractor.itemNotFound walks getCause(), so it still recognises the 404 after executeWithRetries wraps it in a new IOException -- the same reason the existing getTable catch block works.
• A swallowed 404 is logged at INFO with the table/dataset id, so an operator can still see that the delete found nothing.
• The two new tests prepare exactly one mock response, so a retry trips the Verify in the shared mock request. They assert both "did not throw" and "did not retry".
• Verified locally on :sdks:java:io:google-cloud-platform: BigQueryServicesImplTest passes 50/50 with the change. Reverting only the BigQueryServicesImpl change makes both new tests fail with a VerifyException from the retried request, confirming the tests cover the fix.
• No prior PR referenced this issue.

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