fix(bq jdbc): ensure getMoreResults() always moves the cursor

[logachev]

Statement.execute() method when running single-statement that is not properly handling getMoreResults(). For these queries there is no parentJob, so it always skips any meaningful action (close current statement, try to get next job, reset fields if no next job). Moving parentJob non-null check to getNextJob() method. That way it properly resets fields.

Without that, JDBC standard way of fetching all results ((stmt.getMoreResults() == false) && (stmt.getUpdateCount() == -1))
results in infinite loop.

Added 3 tests to validate this behavior for 3 types: TCL/DDL/SELECT.

[gemini-code-assist]

Code Review

This pull request refactors BigQueryStatement by moving the null check for parentJobId into the getNextJob method and removing it from getMoreResults. It also includes a refactor of connection URI constants and adds new integration tests to verify the behavior of getMoreResults for SELECT, INSERT, and TCL statements. A review comment suggests using try-with-resources in the new test code to ensure robust resource management and prevent potential leaks.