Add grouped updates smoke tests for yarn

[bdragon]

Adds smoke tests for yarn and makes some updates to existing smoke tests along the way.

There's a yarn berry workspaces project in this repo, which led me to think it was being used in the tests/smoke-yarn-berry-workspaces.yaml test, but in fact the test was actually running against another repo, https://github.com/dsp-testing/dependabot-core-6432. To avoid confusion, I updated the smoke test to use the workspaces project included in this repo (dependabot/smoke-tests).

[brrygrdn]

Apologies @bdragon I overlooked reviewing this - it looks like we need to fix a conflict in the run-all script but thanks for adding thorough grouping tests for the different combinations 👍🏻 🚀

[jeffwidman]

@bdragon any idea if the tests this adds are already covered since you put this up? Or does it still add new ones?

I don't mind picking it up to fix merge conflicts and get it across the line, but thought I'd doublecheck with you first to see if you think it's still worth doing since you have more context.