WIP: surface render results in packagerevisionresources api

[droot]

This PR exposes kpt fn render results in the porch API (packagerevisionresources).

I will update the description with an example payload for the API shortly.

A few things that I plan to do after getting initial feedback on the PR:

• Expose the render results in case of error
• Try out approachs of saving the function results. A few alternatives I want to try out:
  • Save render results in the package itself. API to read the result from the resource in the package.
  • Save render results in the git-commit. Quick look suggests there isn't any limit on the git commit message https://stackoverflow.com/questions/9733757/maximum-commit-message-size, but may depend on the git hosting provider.
  • Add tests

/cc @mortent @justinsb

[droot]

/cc @ChristopherFry

[droot]

Could we add a test of this to make sure we don't accidentally break it?

I enhanced the existing updateResources tests to assert the renderStatus.