kpt fn render should support resource pruning

[droot]

Expected Behavior:
Pkg App has two resources a.yaml and b.yaml and it has a pipeline has one of the mutators that drops the resource b.yaml. So if user runs pipeline run App, b.yaml should be deleted from the local filesystem.

[droot]

Initially I thought using kio.LocalPkgReaderWriter would be enough to solve this problem, but realized it is not because it tracks resources using .Read() but in our case, resources are read as we DFS through the hydration DAG at each pkg level so wont work that way. One possible way to do it will be to track inputResources (filtering out meta resources) in hydrationContext as we DFS, and when we finally write the resource at the top level pkg, write the hydrated resources and then delete the diff(inputResources - hydratedResources).

/cc @frankfarzan @Shell32-Natsu

[droot]

This is addressed with the PR #1589 so closing this.