Summary

Implement fd_renumber for the native and web Preview1 backends.

Parent tracking issue: #15
Suggested implementation order: 18 / 39

References

• https://github.com/WebAssembly/WASI/blob/wasi-0.1/preview1/docs.md#L1882

Acceptance criteria

• fd_renumber no longer returns ENOSYS on native and web.
• Tests cover renumbering and invalid descriptor cases.