Split JmxUtils class into smaller classes with similar responsibilities....

... Each extracted class has at least 80% lign coverage.

This refactoring touches a lot of classes, but is very mechanical and introduces only very limited risk of regression.

This PR touches a fairly large number of files. and can be a bit scary. I did my best to be as un-invasive as possible, but failed to control correctly the changes in the order of imports and some automatic formatting. If this is a problem for the reviewer, I will rework this manually. If you have specific rules about comment formatting and order of imports, I'll be glad to implement a check for them to ensure consistency.
That would break the Dependency Inversion principle (System is about as concrete as it gets) and make the class untestable. Another option would be to go for an object oriented solution, transform prettyPrintJson to an instance method and treat the PrintStream as the configuration of the class.