napi: keep async cleanup hook handles alive until the addon removes them - #37204

Now that this function unconditionally deletes the handle and returns `true`, the `bool` return type carries no information — the sole caller (`napi_remove_async_cleanup_hook` at napi.cpp:3298) already null-checks `handle` and discards the return value. Since this PR rewrote the function body and made the return degenerate, it should become `void` and drop the redundant `if (handle == nullptr) return false;` guard.

The test relies solely on `checkSameOutput` (Bun == Node) without pinning the expected lifecycle lines, so if both runtimes short-circuited identically the test would pass without exercising `napi_remove_async_cleanup_hook`. Since the fixture already prints `status=%d` for this purpose, consider capturing the result and asserting e.g. `expect(result).toContain("async cleanup hook removed: status=0")` and `"tsfn finalize: removing async cleanup hook"` — CodeRabbit's follow-up asked for this and t