Try to find pnpm-lock.yaml file upwards on tree structure

[Yurickh]

What are you trying to accomplish?

Iterate the folder tree upwards in order to find a pnpm-lock file when the directory source points to a nested workspace.

This hopefully addresses #10758, but I'd like to be able to verify these changes against my own repository. Is there any way to point dependabot to a fork in GitHub? I couldn't find any docs on it.

Anything you want to highlight for special attention from reviewers?

I'm not familiar with ruby project standards, so please let me know if you'd rather structure tests or code in a different way. I tried following the existing standards, but might have missed something.

How will you know you've accomplished your goal?

• The test I've added was failing prior to the changes in code, which I hope is enough to reproduce the issue described in Dependabot doesn't work with monorepos using pnpm #10758.
• I'd like to test these changes against my own repository, but couldn't find a way to point dependabot to a fork.

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.