[keshavdandeva]

Summary

ITAuthTests, ITBigQueryJDBCTest, ITJdbcTimestampPicosTest and ITPcntTest are in both
ITPresubmitTests and ITNightlyTests. Kokoro bq_drivers_v2 runs both suites together,
so these classes run twice in parallel and write report files with the same name. The last one
to finish overwrites the other: in Kokoro integration #112 and proxy #111, build.log shows a
test failure but the published test results show none.

Changes

• ITNightlyTests: keep only ITNightlyBigQueryTest and ITOpenTelemetryTest.
• .cloudbuild/scripts/jdbc-nightly.sh: run ITPresubmitTests,ITNightlyTests so the Cloud Build
  nightly still runs the 4 classes removed from ITNightlyTests.

Effect

• Kokoro bq_drivers_v2: no config change; each class runs once and is reported once.
• Cloud Build PR presubmit (ITPresubmitTests): unchanged.
• Cloud Build nightly: keeps its previous classes and also runs the presubmit-only classes, so it takes longer.

[gemini-code-assist]

Code Review

This pull request updates the nightly integration test configuration. In jdbc-nightly.sh, it configures the integration tests to run both ITPresubmitTests and ITNightlyTests. In ITNightlyTests.java, it removes several test classes that are already covered by ITPresubmitTests to avoid duplication, and adds a Javadoc comment explaining this change. There are no review comments to address.