refactor(bigquery): move bigquerystorage integration tests to java-bigquery

[jinseopkim0]

Summary

Move the 11 end-to-end integration test classes (95 @Test methods) and helper utilities from java-bigquerystorage into java-bigquery (google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/storage/).

Rationale

• java-bigquerystorage is a high-throughput streaming data-plane client. It does not have Control Plane RPCs to create or delete BigQuery datasets or tables.
• The 95 integration tests rely on java-bigquery (com.google.cloud.bigquery.BigQuery) to create temporary test tables in GCP and force-delete them after execution.
• Since java-bigquery already has a compile dependency on java-bigquerystorage, moving these integration tests into java-bigquery resolves the circular test dependency cleanly while preserving 100% of the end-to-end integration test coverage.
• java-bigquerystorage retains 398 unit tests (across 37 test classes) that run offline against local mock gRPC servers.

[gemini-code-assist]

Code Review

This pull request removes the google-cloud-bigquery test dependency from the java-bigquerystorage/google-cloud-bigquerystorage/pom.xml file. There are no review comments, and I have no feedback to provide.