chore(bqjdbc): helper tools

[logachev]

Environments:

• Terraform script to deploy GCE VM with configured Private Service Connect. Can be used to validate PSC properties in JDBC driver.

Tools:

• Client: allows to run custom queries or metadata methods with various connection strings to debug the driver. Also makefile simplifies capturing JFR to analyze performance.
• Perf: python script that leverages Client to run custom queries and compare perf between different driver versions. Allows to customize # of rows, columns, iterations & use rest or read api.

More details are in README docs for each tool

[gemini-code-assist]

Code Review

This pull request adds a suite of tools for the BigQuery JDBC driver, including a Java-based client, performance benchmarking scripts, and Terraform configurations for Private Service Connect environments. Key feedback includes implementing try-with-resources for better resource management in the Java client, using System.nanoTime() for more accurate performance metrics, removing hardcoded usernames from Terraform outputs, and improving the portability of the Python performance script.