Thorough Groovy indy tests

It turns out that Groovy does not simply use invokedynamic when using the -indy jar. It requires
explicit invokedynamic configuration, too. This means that most Groovy applications in the wild do
not use invokedynamic, unless they have been compiled with explicit indy support.

I added more tests with and without Groovy invokedynamic. The comparison is "funny".
Ability to skip awfully slow tests
Full Nashorn bench