[JENKINS-26481] Generate CpsDefaultGroovyMethods, invoke using GroovyCategorySupport

[jglick]

I accidentally merged #54 and it seems GitHub offers no way to unmerge a PR.

Pulls the category trick down from jenkinsci/workflow-cps-plugin#124 (and should become upstream of that if all works out).

Implements #7, picking up artifacts from cloudbees/groovy-cps-dgm-builder#4 (ideally this would be automated by Maven but for now it is manual).

Supersedes #52 (though the expanded tests could be sideported).

@reviewbybees

[abayer]

I was wondering what happened there...

[abayer]

So I think we need sort - it's too obvious a method to use once we've got each, collect, etc... I know it's some work, but I think of the things that are not yet translated, that's the most important.

I'm also not sure whether we should hold this until StringGroovyMethods is ready too - I think we can probably wait on it, but it feels like we might as well do it now while we're here?

[jglick]

Well I do not know how to implement sort so my feeling is that if @kohsuke wants to take it on some time, great, else we do not do it. (It would have been easier had the translation tool been written to reuse CpsTransformer, treating its Java input as Groovy code except in special cases like new arrays with initializers, but instead it is a separate beast, and quite hard to work on.)

W.r.t. StringGroovyMethods, if you feel like writing a test for it now, I should be able to include it pretty easily (if all goes well), but I am guessing it is rarely used so I was not going to hold things up for that.

[abayer]

Ok, sounds reasonable on both counts.

[jglick]

@reviewbybees done