Add LambdaMetafactory support for Method Invokers

[shalearkane]

This adds

• LambdaInvoker and FixedLambdaInvoker for efficiently invoking parameter-less class methods (or simple getters)
• minimum 8% performance improvements for queries invoking such class methods

However, this code fails for static parameter-less methods. In case of failure to create a LambdaInvoker, it falls back to creating a MethodInvoker. There is no performance hit as this happens during initialisation.

This change is inspired by GraphQL-Java's Improved Data Fetching implemented at LambdaFetchingSupport based on LambdaMetafactory.