codeeditor: test (failing) for global var assignment
testframework: onTearDown callbacks
codeeditor: cleanup for testEvalGlobalVarAssignment
eval fix: This reverts some of the changes introduced in #64357fc and #d5a34c1
and moves them into an own module that can be loaded while these features are
under development. Use Config.set('improvedJavaScriptEval', true) to activate
those changes

relevant for issue #158