[turbopack]: Use tip-of-branch for benchmarks (#50615)
With vercel/turbo#5156, we'll be able to install our the locally built `next` package. Before, we'd test the tip-of-branch `next-dev` binary against the last cut `next` canary, which causes headaches when we make breaking changes.
With this PR, we'll now test tip-of-branch `next-dev` binary against a tip-of-branch `next` package, and breaking changes can be properly benched.
Fixes WEB-1133
