test: re-enable and fix timed-out unit tests in PublisherImplTest

[michaelpri10]

Fixes #13051

[gemini-code-assist]

Code Review

This pull request re-enables the testResumePublish and testPublishThrowExceptionForUnsubmittedOrderingKeyMessage tests in PublisherImplTest.java which were previously disabled. The testResumePublish test was updated to use a fake executor for the publisher service implementation. Review feedback suggests that testPublishThrowExceptionForUnsubmittedOrderingKeyMessage should also be updated to use the same fake executor configuration to ensure consistency and prevent potential timeout issues.

[gemini-code-assist]

The test testResumePublish was updated to include testPublisherServiceImpl.setExecutor(fakeExecutor); to resolve timeout issues. It appears that testPublishThrowExceptionForUnsubmittedOrderingKeyMessage might require a similar configuration to ensure the mock service uses the same fake executor, especially since it is also being re-enabled after previously timing out.

    testPublisherServiceImpl.setExecutor(fakeExecutor);
    Publisher publisher =
        getTestPublisherBuilder()