Drop support for older Java versions in debugger

Same as https://github.com/eclipse-jdt/eclipse.jdt.ui/issues/1465 but for JDT Debug component.

We should follow-up the jdt.core issue https://github.com/eclipse-jdt/eclipse.jdt.core/issues/2536 with support in the JDT Debug as well. This issue is to discuss and track the corresponding debugger changes. To start with, we should remove the older versions of JEs and compliance levels from the UI.

The other issue that is kind of related but might be worth taking up is the ordering of the compliance levels. As we focus more on support for more recent Java versions, it doesn't make sense to stick to the older-versions-first approach on the UI drop down list. Perhaps, we should revert the order to reflect the trend in usage.

Example for the old EE's is properties of the JRE container on a project:


also a "new Java project" and similar wizards:

What is not clear for me if this page should also filter possible EE's (why should it if they can't be used for projects, but of course there are bundles around that have old EE's specified):