Build: Fix benchmark to run on local packages

[shilman]

Issue: N/A

What I did

Alternative to #19797 to make sure bench runs against local package versions by reusing sandbox logic for configuring yarn2. This version benchmarks a clean project version so that the benchmarks don't change as we add more stories/addons to the sandboxes.

• Extend sandbox to be able to target a different root directory
• Add --skip-template-stories to sandbox
• Update bench CI config

How to test

• CI passes

[tmeasday]

Yes, I see, it makes sense to use a consistent, unchanging set of stories for the benches. WFM.