[NEXT-1228] Adding hidden form input at start of form overrides ACTION_ID when using server action

[mgm1313]

Verify canary release

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

Provide environment information

Operating System:
      Platform: linux
      Arch: x64
      Version: #22 SMP Tue Jan 10 18:39:00 UTC 2023
    Binaries:
      Node: 16.17.0
      npm: 8.15.0
      Yarn: 1.22.19
      pnpm: 7.1.0
    Relevant packages:
      next: 13.4.4-canary.0
      eslint-config-next: N/A
      react: 18.2.0
      react-dom: 18.2.0
      typescript: 4.9.5

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

App directory (appDir: true)

Link to the code that reproduces this issue or a replay of the bug

https://codesandbox.io/p/sandbox/gracious-http-zqknr4

To Reproduce

Create a form with a server action. Add a hidden input as the direct child of the form.

Describe the Bug

When adding a hidden form input at the start of a form, it appears twice in the DOM and the posted data to the server action. With it, the automatically inserted hidden $ACTION_ID seems to get overwritten.
When moving the input to the bottom of the form, all is working fine.

<form action="" enctype="multipart/form-data" method="POST">
  <input type="hidden" name="pathname" value="/">
  <input type="hidden" name="pathname" value="/">
  <input type="text" name="Enter your name">
  <button type="submit">Submit</button>
</form>

Expected Behavior

<form action="" enctype="multipart/form-data" method="POST">
  <input type="hidden" name="$ACTION_ID_f9fae9b99644f9d4fb5dcdfdb8fb0e06af189eef">
  <input type="hidden" name="pathname" value="/">
  <input type="text" name="Enter your name">
  <button type="submit">Submit</button>
</form>

Which browser are you using? (if relevant)

No response

How are you deploying your application? (if relevant)

No response

_NEXT-1228

[github-actions]

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