Adds missing wp_salt() and wp_generate_uuid4() stubs to BaseTestCase::setUp()
so tests that call PRAutoBlogger_Encryption (for API key decryption) don't fail.
Fixes PublisherTest::test_publish_links_generation_logs_by_run_id() which was
capturing the wrong database query (SELECT from SourceCollector) due to test
fixture including source_ids. Now creates a fixture override without source_ids
to isolate the run_id linking assertion.
Related: Failures #1 and #2 from PR #109.
5a5b00f735