Improve the java agnet configuration to cover the config file

[tanaka-takayoshi]

How can we make our docs better?

There a lot of missing configuration items that are specified in the config file (included in Agent zip binary) but not described in the doc.

A customer is confusing how to use these missing configurations.

[github-actions]

Hi @tanaka-takayoshi 👋

Thank you for filing an issue! We'll triage your issue and let you know if we have questions, and then route it to the appropriate team so we can get it solved.