"Fat-free Lambdas"

Hi folks,

Donald Raab of Eclipse Collections fame, did a recent blog post about
what that library has done for better performance:

https://donraab.medium.com/fat-free-lambdas-in-java-bf228da0613b

Donald sent me a private message asking about Groovy's take on some of
those optimisations, so I thought it might be interesting to analyse
things. Past optimisation work, and the recent work Daniel did on
optimizing non-capturing lambdas put Groovy on a good footing for some
metrics but for many of our DGM methods that take Closures, we have
ways (with varying degrees of impact) to make things more performant.

I did a benchmark and the results are in:

https://issues.apache.org/jira/browse/GROOVY-12034

There is a PR but currently the PR is just the benchmark tests
themselves, not any code changes at present:

https://github.com/apache/groovy/pull/2557

I'd encourage folks to read that ticket, we have a few options we
might want to explore.

TL;DR
* there are a few potential optimsations we might be able to apply for
existing code
* we might want to consider a curryWith method, kind of a lazy rcurry
* we might want to consider the equivalent of Eclipse Collections
"*With" method variants. Instead of "words.findAll{ it.startsWith('A')
}" we'd have a variant "words.findAll(String::startsWith, 'A')

Anyway, I'll ponder things a bit more and make some follow-up
PRs/emails. The analysis suggests just creating the extra variants on
a handful of the most widely used DGM methods. But feedback is most
welcome.

Cheers, Paul.