We should add a "wrappers" section for specifying things like withCredentials, timeout and the like across the entire build rather than just within the steps for a given stage.

A couple notes - this will need to only be for block-scoped Pipeline steps, not for BuildWrapper, since the latter require a node context. And this'll be a little tricky to implement since we want to be able to specify a wrapper step and any of its arguments and then invoke each of those steps with the rest of the build (including subsequent wrapper steps) in a closure passed to those steps...