Add some docs re working with java agents and JBoss Modules

The Admin Guide should include discussion of using Java Agents with WildFly, specifically how to use the MODULES-393 features, and some mention of the types of problems that led to implementing that. IF MODULES-393 won't solve some of those problems, discussion of that would be good.

A likely spot for this is right after https://docs.wildfly.org/25/Admin_Guide#Command_line_parameters

The Getting Started Guide should probably have a brief "for more information" section that links to the new section, and also to the existing Admin_Guide#Command_line_parameters.