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.