add directory to existing PR checks, updating tests

[jakecoffman]

What are you trying to accomplish?

Similar to #10320, we need to update the tests to add directory for existing-pull-requests data to ensure we're testing what's being used in production from now on.

This revealed a few errors and some missed coverage.

Anything you want to highlight for special attention from reviewers?

Unlike #10320, the files involved here are not using DependencyChange, and are not multi-dir aware. So they use job.source.directory since there can only be one directory involved.

How will you know you've accomplished your goal?

The silent e2e tests here are reliable so I don't feel the need to reproduce this behavior in a repo.

Checklist

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested my code changes to ensure they work as expected, including adding additional tests for new functionality.
• I have written clear and descriptive commit messages.
• I have provided a detailed description of the changes in the pull request, including the problem it addresses, how it fixes the problem, and any relevant details about the implementation.
• I have ensured that the code is well-documented and easy to understand.