Turbopack: restrict server HMR to app pages (#90663)
App router types like routes go through the traditional `require` route
bypassing the Turbopack runtime, so they aren't easily solved with
server HMR right now.
Test Plan: Added an e2e test.
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Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>
