Add puppet-runtime PR test to report on which projects are affected by the changes

Platform OS (and other teams that interact with puppet-runtime) have had some difficulties in quickly and easily getting a clear picture of which components (and which versions of those components) are available in each puppet-runtime project. We'd like to be able to report this information in a PR check of some kind so that appropriate teams can be review-requested right away.

Vanagon produces a BOM file like this one. Build a Jenkins job that comments on new pull requests to puppet-runtime with:

• Which projects will be affected by the changes in the PR, and
• Any updates to component versions that will happen in these projects

This will let us know right away which teams should be asked for reviews before merging.