feat(ext/node): implement node:wasi - #34089

## Summary

Implements the `node:wasi` polyfill, taking over
[denoland#32413](denoland#32413).

- Adds `ext/node/ops/wasi.rs`: a `WasiContext` cppgc object exposing the
WASI preview1 ABI (args/env, clocks, random, fd_*, path_*, sched_yield)
backed by `std::fs` + `std::io::stdin/stdout/stderr`. Path-based ops
resolve against preopened directories and are gated by Deno's
`PermissionsContainer` (`OpenAccessKind::Read|Write|ReadWrite`) on the
canonicalized path, refusing to escape the preopen root.
- Rewrites `ext/node/polyfills/wasi.ts` from a stub to a full `WASI`
class (constructor option validation, `wasiImport`, `getImportObject`,
`start`, `initialize`) that delegates to `WasiContext`. Cross-VM-context
support uses `Object.prototype.toString` for `WebAssembly.Memory`
checks.
- Lazy loaded: `wasi.ts` is registered via `lazy_loaded_js`, fronted by
the existing thin `wasi_esm.ts` synthetic-ESM wrapper. The Rust ops
aren't reachable until something actually imports `node:wasi`.
- Adds `ERR_WASI_NOT_STARTED` (Node parity).
- Enables `wasi/test-wasi-options-validation.js`,
`wasi/test-wasi-start-validation.js`,
`wasi/test-wasi-initialize-validation.js` in the node_compat suite, and
removes `wasi` from `IGNORED_TEST_DIRS` so they're discovered.
- Adds `tests/unit_node/wasi_test.ts` with 14 cases covering the
constructor, `getImportObject`, real WASM `start`/`initialize`, and the
import-object surface area.

Closes denoland#24289
Closes denoland#21025
Closes denoland/orchid#93

## Notes

- Other `tests/node_compat/runner/suite/test/wasi/*` tests aren't
enabled because they go through
`tests/node_compat/runner/suite/test/fixtures/wasi-preview-1.js`, which
calls `common.expectWarning('ExperimentalWarning', ...)` for Node's WASI
experimental warning. Deno doesn't emit that warning, so the fixture
itself fails before the WASM runs. Enabling those tests is orthogonal to
the WASI implementation and would require either a `expectWarning` shim
or filtering at the fixture layer.
- `poll_oneoff`, `sock_*`, `proc_raise`, `path_filestat_set_times`,
`fd_filestat_set_times` return `ERRNO_NOSYS` — sufficient for the
validation tests and the WASI interface surface, can be implemented
incrementally as compat tests get enabled.

## Test plan

- [x] `cargo test unit_node::wasi_test` — 14 tests pass
- [x] `cargo test --test node_compat -- wasi-options-validation` — pass
- [x] `cargo test --test node_compat -- wasi-start-validation` — pass
- [x] `cargo test --test node_compat -- wasi-initialize-validation` —
pass
- [x] `./x lint` — clean
- [x] `./x fmt` — clean

Co-authored-by: divybot <[email protected]>
Co-authored-by: Divy Srivastava <[email protected]>
Co-authored-by: Kaju <[email protected]>
Co-authored-by: Bartek Iwańczuk <[email protected]>