fix(ext/node): support numeric FDs in child_process stdio array (#33140)
## Summary
Now that `fs.openSync` returns real OS file descriptors (#33039),
numeric values in child_process stdio arrays should be treated as raw fds rather
than Deno resource IDs. This re-lands the functionality from #32959
(reverted in #33017) with the correct fd-based approach.
- Rename `StdioOrRid` to `StdioOrFd`, replace `Rid(ResourceId)` with
`Fd(i32)`
- `as_stdio()` dups the fd directly (`libc::dup` on Unix, handle clone
on Windows) instead of looking up the resource table
- `extra_stdio` now accepts `StdioOrFd` so numeric fds work beyond
stdin/stdout/stderr
- Hardcoded `Rid(1)`/`Rid(2)` for inherit become `Fd(1)`/`Fd(2)`
- Remove unused `FileResource` import
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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>