feat: Supports the same setup way as the Gradle plug-in

[junghoon-vans]

For the checkstyle gradle plug-in, the default path for the configuration files is specified in the ./config/checkstyle.
Our tools will support the same approach to make setup easier.

This requires the following tasks.

• Change default path of configuration files to ./config/checkstyle.
• Scan ${config_loc} in suppresions.xml.