Server action redirect with absolute internal URL duplicates basePath

[sk-1982]

Link to the code that reproduces this issue

https://github.com/sk-1982/nextjs-absolute-url-redirect-basepath-bug

To Reproduce

1. Clone and start the app
2. Visit localhost:3000/web
3. Click the "Absolute URL Redirect" button

Current vs. Expected behavior

Current: Clicking the "Absolute URL Redirect" button sends the user to a 404 page. Reloading the page shows the correct test page. This is because #60798 made redirects with absolute internal URLs identical to relative URLs. However, this does not consider that the absolute URL will contain basePath. As a result, the redirect is equivalent to redirect('/web/test'), which resolves to http://localhost:3000/web/web/test (which doesn't exist).

Expected: redirects with an absolute internal URL should remove the base path and correctly redirect.

Provide environment information

Operating System:
  Platform: win32
  Arch: x64
  Version: Windows 10 Pro
  Available memory (MB): 32680
  Available CPU cores: 24
Binaries:
  Node: 21.1.0
  npm: N/A
  Yarn: N/A
  pnpm: N/A
Relevant Packages:
  next: 14.3.0-canary.4 // Latest available version is detected (14.3.0-canary.4).
  eslint-config-next: N/A
  react: 18.2.0
  react-dom: 18.2.0
  typescript: 5.1.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Routing (next/router, next/navigation, next/link)

Which stage(s) are affected? (Select all that apply)

next dev (local), next start (local), Vercel (Deployed), Other (Deployed)

Additional context

Also see related issue: #64413

[github-actions]

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