[NEXT-1163] App dir dynamic routes treats '%2F' in page params as '/' when deployed to Vercel

Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

Operating System:
      Platform: darwin
      Arch: x64
      Version: Darwin Kernel Version 22.4.0: Mon Mar  6 21:00:17 PST 2023; root:xnu-8796.101.5~3/RELEASE_X86_64
    Binaries:
      Node: 19.6.0
      npm: 9.4.0
      Yarn: 1.22.18
      pnpm: 7.27.0
    Relevant packages:
      next: 13.4.2-canary.5
      eslint-config-next: 13.3.4
      react: 18.2.0
      react-dom: 18.2.0
      typescript: 5.0.4

Which area(s) of Next.js are affected? (leave empty if unsure)

No response

Link to the code that reproduces this issue

https://github.com/eBakken/next-13-page-params

To Reproduce

Clone repo and deploy to Vercel.

It can also be seen here:
https://next-13-page-params.vercel.app/app/foo/bar/foo%2Fbar

Describe the Bug

Dynamic routing in /app directory treats %2F as /.

encodeURIComponent("foo/bar") gives "foo%2Fbar"

But the page params for the URL /foo/bar/foo%2Fbar gives ["foo","bar","foo","bar"] when deployed to Vercel.
See https://next-13-page-params.vercel.app/app/foo/bar/foo%2Fbar

The problem does not appear locally when running yarn dev.

Expected Behavior

I would expect the behavior to be the same as when using /pages: ["foo","bar","foo/bar"].
See https://next-13-page-params.vercel.app/pages/foo/bar/foo%2Fbar

Which browser are you using? (if relevant)

No response

How are you deploying your application? (if relevant)

Vercel

_NEXT-1163

Start with the linked next-13-page-params reproduction and compare the deployed /app and /pages routes using the encoded foo%2Fbar URL. Reproduce the difference locally and on Vercel, then trace the app-directory dynamic route parameter handling; done means the deployed app route preserves foo/bar as one parameter, matching /pages.