Runner self-updates don't preserve symlinks in externals

Describe the bug
When the self-updater recursively copies files from the update tarball into the root file system, it does so without paying attention to whether a file is a symlink.

In particular, the the npm, npx, and corepack symlinks bundled with Node.js are resolved to actual files. JS actions that aim to be portable across public runners and self-hosted runners (where Node.js isn't provided by the OS) that depend on these binaries being in the PATH stop working.

To Reproduce
Steps to reproduce the behavior:

1. Host a self-hosted runner on a version older than 2.296.1
2. Run an action that adds your runner's externals/node16/bin directory to the PATH
3. Run a step that executes corepack enable or npm
4. See error

Expected behavior
The loop here should handle when the file being copied is a symlink:

https://github.com/actions/runner/blob/352f201c6257e37b330df1b443ab734856fefb68/src/Runner.Sdk/Util/IOUtil.cs#L368-L380

Runner Version and Platform

Runner 2.296.0 (self-updating to 2.296.1)
Linux x64 (using https://github.com/actions-runner-controller/actions-runner-controller)

What's not working?

I can't execute corepack, but based on my testing, npm/npx seems to be broken too. The updated externals have the full binaries installed rather than symlink causing the following downstream issue: https://github.com/nodejs/node/issues/42791#issuecomment-1104099469

Job Log Output

Here's a snippet of an action that attempts to install corepack symlinks to a temporary directory:

/runner/externals/node16/bin/corepack enable --install-directory /runner/_work/_temp/7ed1e9df-f2bf-4ab2-8ba0-93e93ceddb93
  Internal Error: Cannot find module 'corepack/package.json'
  Require stack:
  - /runner/externals.2.296.1/node16/bin/corepack
  Require stack:
  - /runner/externals.2.296.1/node16/bin/corepack
      at Function.Module._resolveFilename (node:internal/modules/cjs/loader:933:15)
      at Function.resolve (node:internal/modules/cjs/helpers:10[8](https://github.com/****/runs/8140449464?check_suite_focus=true#step:4:10):1[9](https://github.com/****/runs/8140449464?check_suite_focus=true#step:4:11))
      at EnableCommand.execute (/runner/externals.2.296.1/node16/bin/corepack:3332:46)
      at EnableCommand.validateAndExecute (/runner/externals.2.296.1/node16/bin/corepack:450:37)
      at Cli.run (/runner/externals.2.296.1/node16/bin/corepack:144:38)
      at main (/runner/externals.2.296.1/node16/bin/corepack:14823:26)
      at runMain (/runner/externals.2.296.1/node16/bin/corepack:14845:5)
      at /runner/externals.2.296.1/node16/bin/corepack:14857:5
      at /runner/externals.2.296.1/node16/bin/corepack:14859:3
      at Object.<anonymous> (/runner/externals.2.296.1/node16/bin/corepack:14864:[12](https://github.com/****/runs/8140449464?check_suite_focus=true#step:4:14))

Runner and Worker's Diagnostic Logs

NA

Start in src/Runner.Sdk/Util/IOUtil.cs around lines 368-380, where the self-updater recursively copies files from the update tarball. Reproduce the update with a symlink in the externals tree and verify that the copied entry remains a symlink rather than becoming a regular file. Done means npm, npx, and corepack continue to work after self-updating.